Golf balls having at least one layer formed from a plasticized acid copolymer composition

ABSTRACT

The present invention is directed to multi-layer golf balls including a layer formed from a relatively soft or low modulus HNP composition and a layer formed from a relatively hard or high modulus HNP composition. Optionally, the soft (or low modulus) HNP composition and/or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/588,317, filed Dec. 31, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/145,593, filed Dec. 31, 2013, now U.S. Pat. No. 9,427,630, the entire disclosures of which are hereby incorporated herein by reference.

Parent application Ser. No. 14/145,593 is a continuation-in-part of U.S. patent application Ser. No. 13/692,583, filed Dec. 3, 2012, which is a continuation of U.S. patent application Ser. No. 13/169,753, filed Jun. 27, 2011, which is a continuation of U.S. patent application Ser. No. 12/795,295, filed Jun. 7, 2010, now U.S. Pat. No. 7,967,701, which is a continuation of U.S. patent application Ser. No. 12/125,306, filed May 22, 2008, now U.S. Pat. No. 7,731,607, which is a continuation-in-part of U.S. patent application Ser. No. 11/972,240, filed Jan. 10, 2008, now U.S. Pat. No. 7,722,482, and U.S. patent application Ser. No. 11/738,759, filed Apr. 23, 2007, now U.S. Pat. No. 7,517,289, which is a continuation-in-part of U.S. patent application Ser. No. 11/304,863, filed Dec. 15, 2005, now U.S. Pat. No. 7,211,008, the entire disclosures of which are hereby incorporated herein by reference.

Parent application Ser. No. 14/145,593 is also a continuation-in-part of U.S. patent application Ser. No. 13/758,041, filed Feb. 4, 2013, which is a continuation of U.S. patent application Ser. No. 13/329,398, which is a continuation of U.S. patent application Ser. No. 12/697,368, filed Feb. 1, 2010, now U.S. Pat. No. 8,079,920, which is a continuation of U.S. patent application Ser. No. 12/125,260, filed May 22, 2008, now U.S. Pat. No. 7,654,916. U.S. patent application Ser. No. 12/125,260 is a continuation-in-part of U.S. patent application Ser. No. 11/694,007, filed Mar. 30, 2007, now U.S. Pat. No. 7,452,290, which is a continuation of U.S. patent application Ser. No. 11/304,962, filed Dec. 15, 2005, now U.S. Pat. No. 7,207,903. U.S. patent application Ser. No. 12/125,260 is also a continuation-in-part of U.S. patent application Ser. No. 12/048,003, filed Mar. 13, 2008, now abandoned. U.S. patent application Ser. No. 12/125,260 is also a continuation-in-part of U.S. patent application Ser. No. 12/048,021, filed Mar. 13, 2008, now U.S. Pat. No. 8,357,059. The entire disclosure of each of these references is hereby incorporated herein by reference.

Parent application Ser. No. 14/145,593 is also a continuation-in-part of Ser. No. 13/584,167, filed Aug. 13, 2012, which is a continuation of U.S. patent application Ser. No. 13/164,233, filed Jun. 20, 2011, which is a continuation of U.S. patent application Ser. No. 12/125,320, filed May 22, 2008, now U.S. Pat. No. 7,963,862, which is a continuation-in-part of U.S. patent application Ser. No. 11/738,759, filed Apr. 23, 2007, now U.S. Pat. No. 7,517,289, which is a continuation-in-part of U.S. patent application Ser. No. 11/304,863, filed Dec. 15, 2005, now U.S. Pat. No. 7,211,008, the entire disclosures of which are hereby incorporated herein by reference. U.S. patent application Ser. No. 12/125,320 is also a continuation-in-part of U.S. patent application Ser. No. 11/972,259, filed Jan. 10, 2008, now U.S. Pat. No. 7,753,810, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to golf balls comprising a multi-layer core and a cover, wherein the core comprises a layer formed from a relatively soft HNP composition and a layer formed from a relatively hard HNP composition, or a layer formed from a low modulus HNP composition and a layer formed from a high modulus HNP composition. The present invention is not limited by which core layer is formed from the soft (or low modulus) HNP composition and which core layer is formed from the hard (or high modulus) HNP composition, so long as both layers are present in the core of the golf ball. Optionally, the soft (or low modulus) HNP composition or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into two general classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., single layer core and single layer cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material, and a cover.

Golf ball core and cover layers are typically constructed with polymer compositions including, for example, polybutadiene rubber, polyurethanes, polyamides, ionomers, and blends thereof. Ionomers, particularly ethylene-based ionomers, are a preferred group of polymers for golf ball layers because of their toughness, durability, and wide range of hardness values.

Golf ball compositions comprising highly neutralized acid polymers are known. For example, U.S. Patent Application Publication No. 2003/0130434, the entire disclosure of which is hereby incorporated herein by reference, discloses melt-processible, highly-neutralized ethylene acid copolymers and process for making them by incorporating an aliphatic, mono-functional organic acid in the acid copolymer and then neutralizing greater than 90% of all the acid groups present. The use of such compositions in various golf ball layers is disclosed. Also, U.S. Patent Application Publication No. 2005/0148725, the entire disclosure of which is hereby incorporated herein by reference, discloses a highly-resilient thermoplastic composition comprising (a) an acid copolymer, (b) a salt of a high molecular weight, monomeric organic acid; (c) a thermoplastic resin; (d) a cation source; and (e) optionally, a filler. The reference also discloses one-piece, two-piece, three-piece, and multi-layered golf balls comprising the highly-resilient thermoplastic composition.

While various uses for highly neutralized acid polymers in golf balls have been discovered, there continues to be a need in the industry to broaden the applicability of highly neutralized acid polymers to particular golf ball constructions having desirable spin, feel, and COR properties. The present invention provides such golf ball constructions through the use of a layer formed from a plasticized acid copolymer composition.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a golf ball comprising a core and a cover. The core has an overall diameter of from 1.40 inches to 1.60 inches and consists of a center, an intermediate core layer, and an outer core layer. The center has a diameter of from 0.50 inches to 1.50 inches and a center hardness (H) of from 20 Shore C to 90 Shore C. The intermediate core layer has a surface hardness (I) of 40 Shore C or greater. The outer core layer has a surface hardness (S) of from 20 Shore C to 90 Shore C. There is a hardness relationship between H, S, and I wherein H<I and S<I. One of the core layers is formed from a first highly neutralized polymer and another of the core layers is formed from a second highly neutralized polymer. At least one of the first highly neutralized polymer composition and the second highly neutralized polymer composition comprises an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof, an organic acid or salt thereof; and a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition. In a particular aspect of this embodiment, the intermediate core layer is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the second highly neutralized polymer composition is less than the material hardness of the first highly neutralized polymer composition. In another particular aspect of this embodiment, the center is formed from the first highly neutralized polymer composition, the intermediate core layer is formed from the second highly neutralized polymer composition, and the material hardness of the first highly neutralized polymer composition is less than the material hardness of the second highly neutralized polymer composition. In another particular aspect of this embodiment, the center is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the first highly neutralized polymer composition is less than the material hardness of the second highly neutralized polymer composition. In another particular aspect of this embodiment, the center is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the second highly neutralized polymer composition is less than the material hardness of the first highly neutralized polymer composition.

In another embodiment, the present invention is directed to a golf ball consisting essentially of a center, an outer core layer, an inner cover layer, and an outer cover layer. The center has a diameter of from 0.50 inches to 1.30 inches, a center hardness of 50 Shore C or greater, and is formed from a first highly neutralized polymer composition. The outer core layer has a surface hardness of 75 Shore C or greater and is formed from a second highly neutralized polymer composition. At least one of the first highly neutralized polymer composition and the second highly neutralized polymer composition comprises an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof, an organic acid or salt thereof; and a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition. In a particular aspect of this embodiment, the inner cover layer has a material hardness less than the surface hardness of the outer core layer, the modulus of the highly neutralized copolymer of the first highly neutralized polymer composition is at least 10% less than the modulus of the highly neutralized copolymer of the second highly neutralized polymer composition. In another particular aspect of this embodiment, the modulus of the highly neutralized copolymer of second highly neutralized polymer composition is at least 10% less than the modulus of the highly neutralized copolymer of the first highly neutralized polymer composition.

In another embodiment, the present invention is directed to a golf ball comprising a core and a cover. The core has an overall diameter of from 1.40 inches to 1.62 inches and consists of a center, an intermediate core layer, and an outer core layer. The intermediate core layer has a surface hardness less than the surface hardness of the center and the surface hardness of the outer core layer. One of the core layers is formed from a first highly neutralized polymer and another of the core layers is formed from a second highly neutralized polymer. At least one of the first highly neutralized polymer composition and the second highly neutralized polymer composition comprises an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof; an organic acid or salt thereof; and a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition. In a particular aspect of this embodiment, the center has a diameter of from 0.100 inches to 0.750 inches is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the first highly neutralized polymer composition is less than the material hardness of the second highly neutralized polymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the second highly neutralized polymer composition is less than the material hardness of the first highly neutralized polymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches is formed from the first highly neutralized polymer composition, the intermediate core layer is formed from the second highly neutralized polymer composition, and the material hardness of the second highly neutralized polymer composition is less than the material hardness of the first highly neutralized polymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches, the intermediate core layer is formed from the first highly neutralized polymer composition, the outer core layer is formed from the second highly neutralized polymer composition, and the material hardness of the first highly neutralized polymer composition is less than the material hardness of the second highly neutralized polymer composition.

In the above embodiments, the highly neutralized composition comprising an acid copolymer, a non-acid polymer, an organic acid or salt thereof, and a cation source optionally has one or more of the following properties:

-   -   (a) the acid copolymer does not include a softening monomer;     -   (b) the acid of the acid copolymer is selected from acrylic acid         and methacrylic acid;     -   (c) the non-acid polymer is an alkyl acrylate rubber selected         from ethylene-alkyl acrylates and ethylene-alkyl methacrylates;     -   (d) the non-acid polymer is present in an amount of greater than         50 wt %, based on the combined weight of the acid copolymer and         the non-acid polymer;     -   (e) the non-acid polymer is present in an amount of 20 wt % or         greater, based on the total weight of the highly neutralized         composition;     -   (f) the non-acid polymer is present in an amount of less than 50         wt %, based on the combined weight of the acid copolymer and the         non-acid polymer;     -   (g) the highly neutralized polymer composition has a solid         sphere compression of 40 or less and a coefficient of         restitution of 0.820 or greater;     -   (h) the highly neutralized polymer composition has a solid         sphere compression of 100 or greater and a coefficient of         restitution of 0.860 or greater;     -   (i) the organic acid salt is a metal salt of oleic acid;     -   (j) the organic salt is magnesium oleate;     -   (k) the organic salt is present in an amount of 30 parts or         greater, per 100 parts of acid copolymer and non-acid copolymer         combined; and     -   (l) the cation source is present in an amount sufficient to         neutralize 110% or greater of all acid groups present in the         composition.

In another embodiment, the present invention is directed to a golf ball comprising a core and a cover. The core has an overall diameter of from 1.40 inches to 1.60 inches and consists of a center, an intermediate core layer, and an outer core layer. The center has a diameter of from 0.50 inches to 1.50 inches and a center hardness (H) of from 20 Shore C to 90 Shore C. The intermediate core layer has a surface hardness (I) of 40 Shore C or greater. The outer core layer has a surface hardness (S) of from 20 Shore C to 90 Shore C. There is a hardness relationship between H, S, and I wherein H<I and S<I. One of the core layers comprises a first acid copolymer composition and another of the core layers comprises a second acid copolymer composition. In a particular aspect of this embodiment, the intermediate core layer comprises the first acid copolymer composition and the outer core layer comprises the second acid copolymer composition. In another particular aspect of this embodiment, the center comprises the first acid copolymer composition and the intermediate core layer comprises the second acid copolymer composition. In another particular aspect of this embodiment, the center comprises the first acid copolymer composition and the outer core layer comprises the second acid copolymer composition. The acid copolymer compositions comprise an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. At least one of the acid copolymer compositions is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized. At least one of the acid copolymer compositions comprises a plasticizer in an amount of from 0.5 wt % to 80 wt %, based on the total weight of the acid copolymer composition. In a particular aspect of this embodiment, the plasticizer is selected from fatty acid esters.

In another embodiment, the present invention is directed to a golf ball consisting essentially of a center, an outer core layer, an inner cover layer, and an outer cover layer. The center has a diameter of from 0.50 inches to 1.30 inches, a center hardness of 50 Shore C or greater, and comprises a first acid copolymer composition. The outer core layer has a surface hardness of 75 Shore C or greater and comprises a second acid copolymer composition. The acid copolymer compositions comprise an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. At least one of the acid copolymer compositions is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized. At least one of the acid copolymer compositions comprises a plasticizer in an amount of from 0.5 wt % to 80 wt %, based on the total weight of the acid copolymer composition. In a particular aspect of this embodiment, the plasticizer is selected from fatty acid esters. In another particular aspect of this embodiment, the inner cover layer has a material hardness less than the surface hardness of the outer core layer. In another particular aspect of this embodiment, the modulus of the acid copolymer of the first acid copolymer composition is at least 10% less than the modulus of the acid copolymer of the second acid copolymer composition. In another particular aspect of this embodiment, the modulus of the acid copolymer of second acid copolymer composition is at least 10% less than the modulus of the acid copolymer of the first acid copolymer composition.

In another embodiment, the present invention is directed to a golf ball comprising a core and a cover. The core has an overall diameter of from 1.40 inches to 1.62 inches and consists of a center, an intermediate core layer, and an outer core layer. The intermediate core layer has a surface hardness less than the surface hardness of the center and the surface hardness of the outer core layer. One of the core layers comprises a first acid copolymer composition and another of the core layers comprises a second acid copolymer composition. The acid copolymer compositions comprise an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. At least one of the acid copolymer compositions is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized. At least one of the acid copolymer compositions comprises a plasticizer in an amount of from 0.5 wt % to 80 wt %, based on the total weight of the acid copolymer composition. In a particular aspect of this embodiment, the plasticizer is selected from fatty acid esters. In another particular aspect of this embodiment, the center has a diameter of from 0.100 inches to 0.750 inches and comprises the first acid copolymer composition, the outer core layer comprises the second acid copolymer composition, and the material hardness of the first acid copolymer composition is less than the material hardness of the second acid copolymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches and comprises the first acid copolymer composition, the outer core layer comprises the second acid copolymer composition, and the material hardness of the second acid copolymer composition is less than the material hardness of the first acid copolymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches and comprises the first acid copolymer composition, the intermediate core layer comprises the second acid copolymer composition, and the material hardness of the second acid copolymer composition is less than the material hardness of the first acid copolymer composition. In another particular aspect of this embodiment, the center has a diameter of from 0.125 inches to 0.750 inches, the intermediate core layer comprises the first acid copolymer composition, the outer core layer comprises the second acid copolymer composition, and the material hardness of the first acid copolymer composition is less than the material hardness of the second acid copolymer composition.

In another embodiment, the present invention is directed to a golf ball consisting essentially of a center, an outer core layer, an inner cover layer, and an outer cover layer. The center has a diameter of from 0.50 inches to 1.30 inches, a center hardness of 50 Shore C or greater, and is formed from a first acid copolymer composition comprising an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. The outer core layer has a surface hardness of 75 Shore C or greater and is formed from a second acid copolymer composition comprising an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. At least one of the acid copolymer compositions is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized. At least one of the acid copolymer compositions comprises a plasticizer in an amount of from 0.5 wt % to 80 wt %, based on the total weight of the acid copolymer composition. In a particular aspect of this embodiment, the plasticizer is selected from fatty acid esters. In another particular aspect of this embodiment, the inner cover layer has a material hardness less than the surface hardness of the outer core layer. In another particular aspect of this embodiment, the modulus of the acid copolymer of the first acid copolymer composition is at least 10% less than the modulus of the acid copolymer of the second acid copolymer composition. In another particular aspect of this embodiment, the modulus of the acid copolymer of second acid copolymer composition is at least 10% less than the modulus of the acid copolymer of the first acid copolymer composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a golf ball according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a golf ball 30 according to one embodiment of the present invention, including a center 32, a first intermediate layer 34, a second intermediate layer 36, and an outer cover layer 38.

Golf balls of the present invention have at least two layers formed from highly neutralized acid polymer (“HNP”) compositions. In a particular embodiment, at least one of the HNP compositions is plasticized. Alternatively, at least one of the layers formed from an HNP composition is replaced by a plasticized acid copolymer composition, wherein less than 80% of the acid groups of the acid copolymer are neutralized. For purposes of the present invention, a composition is “plasticized” if it comprises from at least 0.5 wt %, based on the total weight of the composition, of a plasticizer, as disclosed herein.

In a particular embodiment, golf balls of the present invention have at least one layer formed from a relatively soft, or relatively low modulus HNP composition, and at least one layer formed from a relatively hard, or relatively high modulus HNP composition. In a particular aspect of this embodiment, the relatively soft (or relatively low modulus) HNP composition and/or the relatively hard (or relatively high modulus) HNP composition comprises from 0.5 to 80 wt %, based on the total weight of the composition, of a plasticizer.

As used herein, “highly neutralized acid polymer” refers to an acid polymer after at least 80%, preferably at least 90%, more preferably at least 95%, and even more preferably 100%, of the acid groups of the acid polymer are neutralized.

As used herein, “modulus” refers to flexural modulus as measured using a standard flex bar according to ASTM D790-B. For purposes of the present disclosure, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” Hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value than material hardness. This difference in hardness values is due to several factors including, but not limited to, ball construction (i.e., core type, number of core and/or cover layers, etc.), ball (or sphere) diameter, and the material composition of adjacent layers. It should also be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other. Unless stated otherwise, the hardness values given herein for cover materials are material hardness values measured according to ASTM D2240, with all values reported following 10 days of aging at 50% relative humidity and 23° C.

The surface hardness of a golf ball layer is obtained from the average of a number of measurements taken from opposing hemispheres of a core, taking care to avoid making measurements on the parting line of the core or on surface defects, such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface of a core, care must be taken to insure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for all hardness measurements and is set to take hardness readings at 1 second after the maximum reading is obtained. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand, such that the weight on the durometer and attack rate conform to ASTM D-2240.

The center hardness of a core is obtained according to the following procedure. The core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed. The core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result. The core is secured such that the parting line of the core is roughly parallel to the top of the holder. The diameter of the core is measured 90 degrees to this orientation prior to securing. A measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations. A rough cut, made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool, making sure that the core does not move in the holder during this step. The remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine. The exposed ‘rough’ surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height of the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within ±0.004 inches. Leaving the core in the holder, the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark.

Golf ball core layers of the present invention may have a zero or negative or positive hardness gradient. A hardness gradient is defined by hardness measurements made at the surface of the layer (e.g., center, outer core layer, etc.) and radially inward towards the center of the ball, typically at 2 mm increments. For purposes of the present invention, “negative” and “positive” refer to the result of subtracting the hardness value at the innermost portion of the golf ball component from the hardness value at the outer surface of the component. For example, if the outer surface of a solid core has a lower hardness value than the center (i.e., the surface is softer than the center), the hardness gradient will be deemed a “negative” gradient. In measuring the hardness gradient of a core, the center hardness is first determined according to the procedure above for obtaining the center hardness of a core. Once the center of the core is marked and the hardness thereof is determined, hardness measurements at any distance from the center of the core may be measured by drawing a line radially outward from the center mark, and measuring and marking the distance from the center, typically in 2 mm increments. All hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder. The hardness difference from any predetermined location on the core is calculated as the average surface hardness minus the hardness at the appropriate reference point, e.g., at the center of the core for a single, solid core, such that a core surface softer than its center will have a negative hardness gradient. Hardness gradients are disclosed more fully, for example, in U.S. patent application Ser. No. 11/832,163, filed on Aug. 1, 2007; Ser. No. 11/939,632, filed on Nov. 14, 2007; Ser. No. 11/939,634, filed on Nov. 14, 2007; Ser. No. 11/939,635, filed on Nov. 14, 2007; and Ser. No. 11/939,637, filed on Nov. 14, 2007; the entire disclosure of each of these references is hereby incorporated herein by reference.

Relatively Soft/Low Modulus HNP Composition

Relatively soft HNP compositions of the present invention have a material hardness of 80 Shore D or less, and preferably have a Shore D hardness of 55 or less or a Shore D hardness within the range having a lower limit of 10 or 20 or 30 or 37 or 39 or 40 or 45 and an upper limit of 48 or 50 or 52 or 55 or 60 or 80. Alternatively, soft HNP compositions of the present invention have a material hardness within a range having a lower limit of 30 or 40 or 45 Shore C and an upper limit of 55 or 60 or 80 Shore C.

Low modulus HNP compositions of the present invention comprise at least one low modulus HNP having a modulus within a range having a lower limit of 1,000 or 5,000 or 10,000 psi and an upper limit of 17,000 or 25,000 or 28,000 or 30,000 or 35,000 or 45,000 or 50,000 or 55,000 psi. In a preferred embodiment, the modulus of the low modulus HNP is at least 10% less, or at least 20% less, or at least 25% less, or at least 30% less, or at least 35% less, than the modulus of the high modulus HNP.

Relatively soft HNP compositions of the present invention comprise at least one highly neutralized acid polymer. In a preferred embodiment, the highly neutralized acid polymer of the relatively soft HNP composition is a low modulus HNP having a modulus within a range having a lower limit of 1,000 or 5,000 or 10,000 psi and an upper limit of 17,000 or 25,000 or 28,000 or 30,000 or 35,000 or 45,000 or 50,000 or 55,000 psi. In a particular aspect of this embodiment, the modulus of the low modulus HNP is at least 10% less, or at least 20% less, or at least 25% less, or at least 30% less, or at least 35% less, than that of the high modulus HNP discussed below.

HNPs of the relatively soft/low modulus HNP compositions of the present invention are salts of acid copolymers. It is understood that the HNP may be a blend of two or more HNPs. The acid copolymer of the HNP is an O/X/Y-type copolymer, wherein O is an α-olefin, X is a C₃-C₈ α,β-ethylenically unsaturated carboxylic acid, and Y is a softening monomer. O is preferably ethylene. X is preferably selected from (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, and itaconic acid. (Meth) acrylic acid is particularly preferred. As used herein, “(meth) acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” means methacrylate and/or acrylate. Y is preferably an alkyl (meth) acrylate, wherein the alkyl groups have from 1 to 8 carbon atoms. Preferred O/X/Y-type copolymers are those wherein O is ethylene, X is (meth) acrylic acid, and Y is selected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. Particularly preferred O/X/Y-type copolymers are ethylene/(meth) acrylic acid/n-butyl acrylate, ethylene/(meth) acrylic acid/methyl acrylate, and ethylene/(meth) acrylic acid/ethyl acrylate.

The acid copolymer of the HNP typically includes the α-olefin in an amount of at least 15 wt %, or at least 25 wt %, or at least 40 wt %, or at least 60 wt %, based on the total weight of the acid copolymer. The amount of C₃-C₈ α,β-ethylenically unsaturated carboxylic acid in the acid copolymer is typically within a range having a lower limit of 1 or 2 or 4 or 6 or 8 or 10 or 12 or 15 or 16 or 20 wt % and an upper limit of 20 or 25 or 26 or 30 or 35 or 40 wt %, based on the total weight of the acid copolymer. The amount of optional softening monomer in the acid copolymer is typically within a range having a lower limit of 0 or 1 or 3 or 5 or 11 or 15 or 20 wt % and an upper limit of 23 or 25 or 30 or 35 or 50 wt %, based on the total weight of the acid copolymer.

Particularly suitable acid copolymers of the HNP of the relatively soft/low modulus HNP composition include very low modulus ionomer- (“VLMI-”) type ethylene-acid polymers, such as Surlyn® 6320, Surlyn® 8120, Surlyn® 8320, and Surlyn® 9320. Surlyn® ionomers are commercially available from E. I. du Pont de Nemours and Company. Also suitable are DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, ionomeric materials commercially available from E. I. du Pont de Nemours and Company.

Additional suitable acid copolymers are disclosed, for example, in U.S. Patent Application Publication Nos. 2005/0148725, 2005/0020741, 2004/0220343, and 2003/0130434, and U.S. Pat. Nos. 5,691,418, 6,562,906, 6,653,382, 6,777,472, 6,762,246, and 6,815,480, the entire disclosures of which are hereby incorporated herein by reference.

In a preferred embodiment, the HNP of the relatively soft/low modulus HNP composition is formed by reacting an acid copolymer, which is optionally partially neutralized, with a sufficient amount of cation source, in the presence of a high molecular weight organic acid or salt thereof, such that at least 80%, preferably at least 90%, more preferably at least 95%, and even more preferably 100%, of all acid groups present are neutralized. In a particular embodiment, the cation source is present in an amount sufficient to neutralize, theoretically, greater than 100%, or 105% or greater, or 110% or greater, or 115% or greater, or 120% or greater, or 125% or greater, or 200% or greater, or 250% or greater of all acid groups present in the composition. The acid copolymer can be reacted with the high molecular weight organic acid or salt thereof and the cation source simultaneously, or the acid copolymer can be reacted with the high molecular weight organic acid prior to the addition of the cation source.

Suitable high molecular weight organic acids are aliphatic organic acids, aromatic organic acids, saturated monofunctional organic acids, unsaturated monofunctional organic acids, multi-unsaturated monofunctional organic acids, and dimerized derivatives thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, dimerized derivatives thereof, and combinations thereof. Salts of high molecular weight organic acids comprise the salts, particularly the barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, stontium, titanium, tungsten, magnesium, and calcium salts, of aliphatic organic acids, aromatic organic acids, saturated monofunctional organic acids, unsaturated monofunctional organic acids, multi-unsaturated monofunctional organic acids, dimerized derivatives thereof, and combinations thereof. Suitable organic acids and salts thereof are more fully described, for example, in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference.

Suitable cation sources include metal ions and compounds of alkali metals, alkaline earth metals, and transition metals; metal ions and compounds of rare earth elements; silicone, silane, and silicate derivatives and complex ligands; and combinations thereof. Preferred cation sources are metal ions and compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, tin, lithium, and rare earth metals. The acid copolymer may be at least partially neutralized prior to contacting the acid copolymer with the cation source to form the HNP. Methods of preparing ionomers are well known, and are disclosed, for example, in U.S. Pat. No. 3,264,272, the entire disclosure of which is hereby incorporated herein by reference. The acid copolymer can be a direct copolymer wherein the polymer is polymerized by adding all monomers simultaneously, as disclosed, for example, in U.S. Pat. No. 4,351,931, the entire disclosure of which is hereby incorporated herein by reference. Alternatively, the acid copolymer can be a graft copolymer wherein a monomer is grafted onto an existing polymer, as disclosed, for example, in U.S. Patent Application Publication No. 2002/0013413, the entire disclosure of which is hereby incorporated herein by reference.

Relatively soft/low modulus HNP compositions of the present invention optionally contain one or more melt flow modifiers. The amount of melt flow modifier in the composition is readily determined such that the melt flow index of the composition is at least 0.1 g/10 min, preferably from 0.5 g/10 min to 10.0 g/10 min, and more preferably from 1.0 g/10 min to 6.0 g/10 min, as measured using ASTM D-1238, condition E, at 190° C., using a 2160 gram weight.

Suitable melt flow modifiers include, but are not limited to, high molecular weight organic acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof. Suitable organic acids are aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated monofunctional organic acids, multi-unsaturated mono-functional organic acids, and dimerized derivatives thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, dimerized derivatives thereof. Suitable organic acids are more fully described, for example, in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, the HNP composition comprises an organic acid salt in an amount of 20 phr or greater, or 25 phr or greater, or 30 phr or greater, or 35 phr or greater, or 40 phr or greater.

Additional melt flow modifiers suitable for use in compositions of the present invention, include the non-fatty acid melt flow modifiers described in copending U.S. patent application Ser. Nos. 11/216,725 and 11/216,726, the entire disclosures of which are hereby incorporated herein by reference.

Relatively soft/low modulus HNP compositions of the present invention optionally include additive(s) and/or filler(s) in an amount of 50 wt % or less, or 30 wt % or less, or 15 wt % or less, based on the total weight of the relatively soft/low modulus HNP composition. Suitable additives and fillers include, but are not limited to, chemical blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nano-fillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, TiO₂, acid copolymer wax, surfactants, and fillers, such as zinc oxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc carbonate, barium carbonate, clay, tungsten, tungsten carbide, silica, lead silicate, regrind (recycled material), and mixtures thereof. Suitable additives are more fully described in, for example, U.S. Patent Application Publication No. 2003/0225197, the entire disclosure of which is hereby incorporated herein by reference.

Relatively soft/low modulus HNP compositions of the present invention optionally contain a high modulus HNP.

In a particular embodiment, the relatively soft/low modulus HNP composition has a moisture vapor transmission rate of 8 g-mil/100 in²/day or less (i.e., 3.2 g-mm/m²·day or less), or 5 g-mil/100 in²/day or less (i.e., 2.0 g-mm/m²·day or less), or 3 g-mil/100 in²/day or less (i.e., 1.2 g-mm/m²·day or less), or 2 g-mil/100 in²/day or less (i.e., 0.8 g-mm/m² day or less), or 1 g-mil/100 in²/day or less (i.e., 0.4 g-mm/m² day or less), or less than 1 g-mil/100 in²/day (i.e., less than 0.4 g-mm/m² day). As used herein, moisture vapor transmission rate (“MVTR”) is given in g-mil/100 in²/day, and is measured at 20° C. and according to ASTM F1249-99. In a preferred aspect of this embodiment, the relatively soft/low modulus HNP composition comprises a low modulus HNP prepared using a cation source which is less hydrophilic than conventional magnesium-based cation sources. Suitable moisture resistant HNP compositions are disclosed, for example, in U.S. Patent Application Publication Nos. 2005/0267240, 2006/0106175 and 2006/0293464, the entire disclosures of which are hereby incorporated herein by reference.

In another particular embodiment, a sphere formed from the relatively soft/low modulus HNP composition has a compression of 80 or less, or 70 or less, or 65 or less, or 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less.

Relatively soft/low modulus HNP compositions of the present invention are not limited by any particular method or any particular equipment for making the compositions. In a preferred embodiment, the composition is prepared by the following process. The acid polymer(s), preferably a VLMI-type ethylene-acid terpolymer, high molecular weight organic acid(s) or salt(s) thereof, and optionally additive(s)/filler(s) are simultaneously or individually fed into a melt extruder, such as a single or twin screw extruder. A suitable amount of cation source is simultaneously or subsequently added such that at least 80%, preferably at least 90%, more preferably at least 95%, and even more preferably at least 100%, of all acid groups present are neutralized. Optionally, the cation source is added in an amount sufficient to neutralize, theoretically, 105% or greater, or 110% or greater, or 115% or greater, or 120% or greater, or 125% or greater, or 200% or greater, or 250% or greater of all acid groups present in the composition. The acid polymer may be at least partially neutralized prior to the above process. The components are intensively mixed prior to being extruded as a strand from the die-head.

Relatively soft/low modulus HNP compositions of the present invention optionally comprise one or more additional polymers, such as partially neutralized ionomers (e.g., as disclosed in U.S. Patent Application Publication No. 2006/0128904, the entire disclosure of which is hereby incorporated herein by reference); bimodal ionomers (e.g., as disclosed in U.S. Patent Application Publication No. 2004/0220343 and U.S. Pat. Nos. 6,562,906, 6,762,246, 7,273,903, 8,193,283, 8,410,219, and 8,410,220, the entire disclosures of which are hereby incorporated herein by reference, and particularly Surlyn® AD 1043, 1092, and 1022 ionomer resins, commercially available from E. I. du Pont de Nemours and Company); ionomers modified with rosins (e.g., as disclosed in U.S. Patent Application Publication No. 2005/0020741, the entire disclosure of which is hereby incorporated by reference); soft and resilient ethylene copolymers (e.g., as disclosed U.S. Patent Application Publication No. 2003/0114565, the entire disclosure of which is hereby incorporated herein by reference); polyolefins; polyamides; polyesters; polyethers; polycarbonates; polysulfones; polyacetals; polylactones; acrylonitrile-butadiene-styrene resins; polyphenylene oxide; polyphenylene sulfide; styrene-acrylonitrile resins; styrene maleic anhydride; polyimides; aromatic polyketones; ionomers and ionomeric precursors, acid copolymers, and conventional HNPs; polyurethanes; grafted and non-grafted metallocene-catalyzed polymers; single-site catalyst polymerized polymers; high crystalline acid polymers; cationic ionomers; natural and synthetic rubbers, including, but not limited to, ethylene propylene rubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic block copolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber, halobutyl rubber, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, natural rubber, polyisoprene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber (such as ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and, more specifically, ethylene-ethyl acrylate, ethylene-methyl acrylate, and ethylene-butyl acrylate), chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and polybutadiene rubber (cis and trans); and combinations thereof. Particular polyolefins suitable for blending include one or more, linear, branched, or cyclic, C₂-C₄₀ olefins, particularly polymers comprising ethylene or propylene copolymerized with one or more C₂-C₄₀ olefins, C₃-C₂₀ α-olefins, or C₃-C₁₀ α-olefins. Particular conventional HNPs suitable for blending include, but are not limited to, one or more of the HNPs disclosed in U.S. Pat. Nos. 6,756,436, 6,894,098, and 6,953,820, the entire disclosures of which are hereby incorporated herein by reference. Additional suitable blend polymers include those described in U.S. Pat. No. 5,981,658, for example at column 14, lines 30 to 56, the entire disclosure of which is hereby incorporated herein by reference. The blends described herein may be produced by post-reactor blending, by connecting reactors in series to make reactor blends, or by using more than one catalyst in the same reactor to produce multiple species of polymer. The polymers may be mixed prior to being put into an extruder, or they may be mixed in an extruder. In a particular embodiment, the HNP composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of greater than 50 wt %, or an amount within a range having a lower limit of 50 or 55 or 60 or 65 or 70 and an upper limit of 80 or 85 or 90, based on the combined weight of the acid copolymer and the non-acid polymer. In another particular embodiment, the HNP composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of less than 50 wt %, or an amount within a range having a lower limit of 10 or 15 or 20 or 25 or 30 and an upper limit of 40 or 45 or 50, based on the combined weight of the acid copolymer and the non-acid polymer.

Particularly suitable relatively soft/low modulus HNP compositions include, but are not limited to, the highly-resilient thermoplastic compositions disclosed in U.S. Patent Application Publication No. 2005/0148725; the highly-neutralized ethylene copolymers disclosed in U.S. Pat. Nos. 6,653,382 and 6,777,472, and U.S. Patent Application Publication No. 2003/0130434; and the highly-resilient thermoplastic elastomer compositions disclosed in U.S. Pat. No. 6,815,480; the entire disclosures of which are hereby incorporated herein by reference.

In a particular embodiment, the relatively soft/low modulus HNP composition is formed by blending an acid polymer, a non-acid polymer, a cation source, and a fatty acid or metal salt thereof. For purposes of the present invention, maleic anhydride modified polymers are defined herein as a non-acid polymer despite having anhydride groups that can ring-open to the acid form during processing of the polymer to form the HNP compositions herein. The maleic anhydride groups are grafted onto a polymer, are present at relatively very low levels, and are not part of the polymer backbone, as is the case with the acid polymers, which are exclusively E/X and E/X/Y copolymers of ethylene and an acid, particularly methacrylic acid and acrylic acid.

In a particular aspect of this embodiment, the acid polymer is selected from ethylene-acrylic acid and ethylene-methacrylic acid copolymers, optionally containing a softening monomer selected from n-butyl acrylate and iso-butyl acrylate. Examples of particularly suitable commercially available acid polymers include, but are not limited to, those given in Table 1 below.

TABLE 1 Melt Index Softening (2.16 kg, Acid Monomer 190° C., Acid Polymer (wt %) (wt %) g/10 min) Nucrel ® 9-1 methacrylic acid n-butyl acrylate 25 (9.0) (23.5) Nucrel ® 599 methacrylic acid none 450 (10.0) Nucrel ® 960 methyacrylic acid none 60 (15.0) Nucrel ® 0407 methacrylic acid none 7.5 (4.0) Nucrel ® 0609 methacrylic acid none 9 (6.0) Nucrel ® 1214 methacrylic acid none 13.5 (12.0) Nucrel ® 2906 methacrylic acid none 60 (19.0) Nucrel ® 2940 methacrylic acid none 395 (19.0) Nucrel ® 30707 acrylic acid none 7 (7.0) Nucrel ® 31001 acrylic acid none 1.3 (9.5) Nucrel ® AE methacrylic acid isobutyl acrylate 11 (2.0) (6.0) Nucrel ® 2806 acrylic acid none 60 (18.0) Nucrel ® 0403 methacrylic acid none 3 (4.0) Nucrel ® 925 methacrylic acid none 25 (15.0) Escor ® AT-310 acrylic acid methyl acrylate 6 (6.5) (6.5) Escor ® AT-325 acrylic acid methyl acrylate 20 (6.0) (20.0) Escor ® AT-320 acrylic acid methyl acrylate 5 (6.0) (18.0) Escor ® 5070 acrylic acid none 30 (9.0) Escor ® 5100 acrylic acid none 8.5 (11.0) Escor ® 5200 acrylic acid none 38 (15.0) A-C ® 5120 acrylic acid none not reported (15) A-C ® 540 acrylic acid none not reported (5) A-C ® 580 acrylic acid none not reported (10) Primacor ® 3150 acrylic acid none 5.8 (6.5) Primacor ® 3330 acrylic acid none 11 (3.0) Primacor ® 5985 acrylic acid none 240 (20.5) Primacor ® 5986 acrylic acid none 300 (20.5) Primacor ® 5980I acrylic acid none 300 (20.5) Primacor ® 5990I acrylic acid none 1300 (20.0) XUS 60751.17 acrylic acid none 600 (19.8) XUS 60753.02L acrylic acid none 60 (17.0)

Nucrel® acid polymers are commercially available from E. I. du Pont de Nemours and Company.

Escor® acid polymers are commercially available from ExxonMobil Chemical Company.

A-C® acid polymers are commercially available from Honeywell International Inc.

Primacor® acid polymers and XUS acid polymers are commercially available from The Dow Chemical Company.

In another particular aspect of this embodiment, the non-acid polymer is an elastomeric polymer. Suitable elastomeric polymers include, but are not limited to:

-   -   (a) ethylene-alkyl acrylate polymers, particularly         polyethylene-butyl acrylate, polyethylene-methyl acrylate, and         polyethylene-ethyl acrylate;     -   (b) metallocene-catalyzed polymers;     -   (c) ethylene-butyl acrylate-carbon monoxide polymers and         ethylene-vinyl acetate-carbon monoxide polymers;     -   (d) polyethylene-vinyl acetates;     -   (e) ethylene-alkyl acrylate polymers containing a cure site         monomer;     -   (f) ethylene-propylene rubbers and ethylene-propylene-diene         monomer rubbers;     -   (g) olefinic ethylene elastomers, particularly ethylene-octene         polymers, ethylene-butene polymers, ethylene-propylene polymers,         and ethylene-hexene polymers;     -   (h) styrenic block copolymers;     -   (i) polyester elastomers;     -   (j) polyamide elastomers;     -   (k) polyolefin rubbers, particularly polybutadiene,         polyisoprene, and styrene-butadiene rubber; and     -   (l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acid polymers include, but are not limited to, Lotader® ethylene-alkyl acrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, and particularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900 commercially available from Arkema Corporation; Elvaloy® AC ethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC 2116, AC3117, AC3427, and AC34035, commercially available from E. I. du Pont de Nemours and Company; Fusabond® elastomeric polymers, such as ethylene vinyl acetates, polyethylenes, metallocene-catalyzed polyethylenes, ethylene propylene rubbers, and polypropylenes, and particularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614, M603, E100, E158, E226, E265, E528, and E589, commercially available from E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenes and ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C 575, A-C 573, A-C 655, and A-C 395, commercially available from Honeywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers, and Amplify® functional polymers, and particularly Amplify® GR 207, GR 208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commercially available from The Dow Chemical Company; Enable® metallocene polyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers, and Vistalon® EPDM rubber, commercially available from ExxonMobil Chemical Company; Starflex® metallocene linear low density polyethylene, commercially available from LyondellBasell; Elvaloy® HP4051, HP441, HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers and Elvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxide polymers, commercially available from E. I. du Pont de Nemours and Company; Evatane® ethylene-vinyl acetate polymers having a vinyl acetate content of from 18 to 42%, commercially available from Arkema Corporation; Elvax® ethylene-vinyl acetate polymers having a vinyl acetate content of from 7.5 to 40%, commercially available from E. I. du Pont de Nemours and Company; Vamac® G terpolymer of ethylene, methylacrylate and a cure site monomer, commercially available from E. I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commercially available from ExxonMobil Chemical Company; Kraton® styrenic block copolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT, commercially available from Kraton Performance Polymers Inc.; Septon® styrenic block copolymers, commercially available from Kuraray Co., Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069, and 556, commercially available from E. I. du Pont de Nemours and Company; Riteflex® polyester elastomers, commercially available from Celanese Corporation; Pebax® thermoplastic polyether block amides, and particularly Pebax® 2533, 3533, 4033, and 5533, commercially available from Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify® ethylene-propylene copolymer elastomers, and Infuse® olefin block copolymers, commercially available from The Dow Chemical Company; Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO 1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially available from ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularly Royaltuf®498 maleic anhydride modified polyolefin based on an amorphous EPDM and Royaltuf®485 maleic anhydride modified polyolefin based on an semi-crystalline EPDM, commercially available from Chemtura Corporation.

Additional examples of particularly suitable commercially available elastomeric polymers include, but are not limited to, those given in Table 2 below.

TABLE 2 Melt Index % Maleic (2.16 kg, 190° C., % Ester Anhydride g/10 min) Polyethylene Butyl Acrylates Lotader ® 3210 6 3.1 5 Lotader ® 4210 6.5 3.6 9 Lotader ® 3410 17 3.1 5 Lotryl ® 17BA04 16-19 0 3.5-4.5 Lotryl ® 35BA320 33-37 0 260-350 Elvaloy ® AC 3117 17 0 1.5 Elvaloy ® AC 3427 27 0 4 Elvaloy ® AC 34035 35 0 40 Polyethylene Methyl Acrylates Lotader ® 4503 19 0.3 8 Lotader ® 4603 26 0.3 8 Lotader ® AX 8900 26 8% GMA 6 Lotryl ® 24MA02 23-26 0 1-3 Elvaloy ® AC 12024S 24 0 20 Elvaloy ® AC 1330 30 0 3 Elvaloy ® AC 1335 35 0 3 Elvaloy ® AC 1224 24 0 2 Polyethylene Ethyl Acrylates Lotader ® 6200 6.5 2.8 40 Lotader ® 8200 6.5 2.8 200 Lotader ® LX 4110 5 3.0 5 Lotader ® HX 8290 17 2.8 70 Lotader ® 5500 20 2.8 20 Lotader ® 4700 29 1.3 7 Lotader ® 4720 29 0.3 7 Elvaloy ® AC 2116 16 0 1

The acid polymer and non-acid polymer are combined and reacted with a cation source, such that at least 80% of all acid groups present are neutralized. The present invention is not meant to be limited by a particular order for combining and reacting the acid polymer, non-acid polymer and cation source. In a particular embodiment, the fatty acid or metal salt thereof is used in an amount such that the fatty acid or metal salt thereof is present in the HNP composition in an amount of from 10 wt % to 60 wt %, or within a range having a lower limit of 10 or 20 or 30 or 40 wt % and an upper limit of 40 or 50 or 60 wt %, based on the total weight of the HNP composition. Suitable cation sources and fatty acids and metal salts thereof are further disclosed above.

In another particular aspect of this embodiment, the acid polymer is an ethylene-acrylic acid polymer having an acid content of 19 wt % or greater, the non-acid polymer is a metallocene-catalyzed ethylene-butene copolymer, optionally modified with maleic anhydride, the cation source is magnesium, and the fatty acid or metal salt thereof is magnesium oleate present in the composition in an amount of 20 to 50 wt %, based on the total weight of the composition.

The relatively soft/low modulus HNP composition optionally comprises from 0.5 wt % to 80 wt % of a plasticizer, based on the total weight of the composition. Suitable plasticizers are disclosed further below.

Relatively Hard/High Modulus HNP Composition

Relatively hard HNP compositions of the present invention have a Shore D hardness of 35 or greater, and preferably have a Shore D hardness of 45 or greater or a Shore D hardness with the range having a lower limit of 45 or 50 or 55 or 57 or 58 or 60 or 65 or 70 or 75 and an upper limit of 80 or 85 or 90 or 95. Alternatively, hard HNP compositions of the present invention have a material hardness within a range having a lower limit of 65 or 70 or 75 Shore C and an upper limit of 85 or 90 or 95 Shore C.

High modulus HNP compositions of the present invention comprise at least one high modulus HNP having a modulus within a range having a lower limit of 25,000 or 27,000 or 30,000 or 40,000 or 45,000 or 50,000 or 55,000 or 60,000 psi and an upper limit of 72,000 or 75,000 or 100,000 or 150,000 psi.

Relatively hard HNP compositions of the present invention comprise at least one highly neutralized acid polymer. In a preferred embodiment, the highly neutralized acid polymer of the relatively hard HNP composition is a high modulus HNP having a modulus within a range having a lower limit of 25,000 or 27,000 or 30,000 or 40,000 or 45,000 or 50,000 or 55,000 or 60,000 psi and an upper limit of 72,000 or 75,000 or 100,000 or 150,000 psi.

HNPs of the relatively hard/high modulus HNP compositions of the present invention are salts of acid copolymers. It is understood that the HNP may be a blend of two or more HNPs. Preferred acid copolymers are copolymers of an α-olefin and a C₃-C₈ α,β-ethylenically unsaturated carboxylic acid. The acid is typically present in the acid copolymer in an amount within a range having a lower limit of 1 or 2 or 4 or 6 or 8 or 10 or 12 or 15 or 16 or 20 wt % and an upper limit of 20 or 25 or 26 or 30 or 35 or 40 wt %, based on the total weight of the acid copolymer. The α-olefin is preferably selected from ethylene and propylene. The acid is preferably selected from (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, and itaconic acid. (Meth) acrylic acid is particularly preferred. In a preferred embodiment, the HNP of the relatively hard HNP composition has a higher level of acid than the HNP of the relatively soft HNP composition.

Suitable acid copolymers include partially neutralized acid polymers. Examples of suitable partially neutralized acid polymers include, but are not limited to, Surlyn® ionomers, commercially available from E. I. du Pont de Nemours and Company; AClyn® ionomers, commercially available from Honeywell International Inc.; and Iotek® ionomers, commercially available from ExxonMobil Chemical Company. Also suitable are DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, ionomeric materials commercially available from E. I. du Pont de Nemours and Company. Additional suitable acid polymers are more fully described, for example, in U.S. Pat. Nos. 6,562,906, 6,762,246, and 6,953,820 and U.S. Patent Application Publication Nos. 2005/0049367, 2005/0020741, and 2004/0220343, the entire disclosures of which are hereby incorporated herein by reference.

In a preferred embodiment, the HNP of the relatively hard/high modulus HNP composition is formed by reacting an acid copolymer, which may already be partially neutralized, with a sufficient amount of cation source, optionally in the presence of a high molecular weight organic acid or salt thereof, such that at least 80%, preferably at least 90%, more preferably at least 95%, and even more preferably 100%, of all acid groups present are neutralized. In a particular embodiment, the cation source is present in an amount sufficient to neutralize, theoretically, greater than 100%, or 105% or greater, or 110% or greater, or 115% or greater, or 120% or greater, or 125% or greater, or 200% or greater, or 250% or greater of all acid groups present in the composition. Suitable cation sources include metal ions and compounds of alkali metals, alkaline earth metals, and transition metals; metal ions and compounds of rare earth elements; silicone, silane, and silicate derivatives and complex ligands; and combinations thereof. Preferred cation sources are metal ions and compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, tin, lithium, and rare earth metals. Metal ions and compounds of calcium and magnesium are particularly preferred. The acid copolymer may be at least partially neutralized prior to contacting the acid copolymer with the cation source to form the HNP. As previously stated, methods of preparing ionomers, and the acid copolymers on which ionomers are based, are disclosed, for example, in U.S. Pat. Nos. 3,264,272, and 4,351,931, and U.S. Patent Application Publication No. 2002/0013413.

Relatively hard/high modulus HNP compositions of the present invention optionally contain one or more melt flow modifiers. The amount of melt flow modifier in the composition is readily determined such that the melt flow index of the composition is at least 0.1 g/10 min, preferably from 0.5 g/10 min to 10.0 g/10 min, and more preferably from 1.0 g/10 min to 6.0 g/10 min, as measured using ASTM D-1238, condition E, at 190° C., using a 2160 gram weight.

Suitable melt flow modifiers include, but are not limited to, high molecular weight organic acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof. Suitable organic acids are aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated monofunctional organic acids, multi-unsaturated mono-functional organic acids, and dimerized derivatives thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, dimerized derivatives thereof. Suitable organic acids are more fully described, for example, in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, the HNP composition comprises an organic acid salt in an amount of 20 phr or greater, or 25 phr or greater, or 30 phr or greater, or 35 phr or greater, or 40 phr or greater.

Additional melt flow modifiers suitable for use in compositions of the present invention, include the non-fatty acid melt flow modifiers described in copending U.S. patent application Ser. Nos. 11/216,725 and 11/216,726, the entire disclosures of which are hereby incorporated herein by reference.

Relatively hard/high modulus HNP compositions of the present invention optionally include additive(s) and/or filler(s) in an amount within a range having a lower limit of 0 or 5 or 10 wt %, and an upper limit of 25 or 30 or 50 wt %, based on the total weight of the relatively hard/high modulus HNP composition. Suitable additives and fillers include those previously described as suitable for the relatively soft HNP compositions of the present invention.

Relatively hard/high modulus HNP compositions of the present invention optionally contain a low modulus HNP.

In a particular embodiment, the relatively hard/high modulus HNP composition has an MVTR of 8 g-mil/100 in²/day or less (i.e., 3.2 g-mm/m² day or less), or 5 g-mil/100 in²/day or less (i.e., 2.0 g-mm/m² day or less), or 3 g-mil/100 in²/day or less (i.e., 1.2 g-mm/m² day or less), or 2 g-mil/100 in²/day or less (i.e., 0.8 g-mm/m² day or less), or 1 g-mil/100 in²/day or less (i.e., 0.4 g-mm/m²-day or less), or less than 1 g-mil/100 in²/day (i.e., less than 0.4 g-mm/m²-day). In a preferred aspect of this embodiment, the relatively hard/high modulus HNP composition comprises a high modulus HNP prepared using a cation source which is less hydrophilic than conventional magnesium-based cation sources. Suitable moisture resistant HNP compositions are disclosed, for example, in copending U.S. patent application Ser. No. 11/270,066 and U.S. Patent Application Publication No. 2005/0267240, the entire disclosures of which are hereby incorporated herein by reference.

In another particular embodiment, a sphere formed from the relatively hard/high modulus HNP composition has a compression of 70 or greater, or 80 or greater, or a compression within a range having a lower limit of 70 or 80 or 90 or 100 and an upper limit of 110 or 130 or 140.

Relatively hard/high modulus HNP compositions of the present invention are not limited by any particular method or any particular equipment for making the compositions. In a preferred embodiment, the composition is prepared by the following process. The acid polymer(s), preferably an ethylene/(meth) acrylic acid copolymer, optional melt flow modifier(s), and optional additive(s)/filler(s) are simultaneously or individually fed into a melt extruder, such as a single or twin screw extruder. A suitable amount of cation source is then added such that at least 80%, preferably at least 90%, more preferably at least 95%, and even more preferably at least 100%, of all acid groups present are neutralized. Optionally, the cation source is added in an amount sufficient to neutralize, theoretically, 105% or greater, or 110% or greater, or 115% or greater, or 120% or greater, or 125% or greater, or 200% or greater, or 250% or greater of all acid groups present in the composition. The acid polymer may be at least partially neutralized prior to the above process. The components are intensively mixed prior to being extruded as a strand from the die-head.

In another preferred embodiment, the relatively hard/high modulus HNP composition is formed by combining a low modulus HNP with a sufficient amount of one or more additional material(s), including, but not limited to, additives, fillers, and polymeric materials, to increase the modulus such that the resulting composition has a modulus as described above for the high modulus HNP.

Relatively hard/high modulus HNP compositions of the present invention may be blended with one or more additional polymers, such as thermoplastic polymers and elastomers.

Examples of thermoplastic polymers and elastomers suitable for blending include those previously described as suitable for blending with the relatively soft/low modulus HNP compositions of the present invention. In a particular embodiment, the relatively hard/high modulus HNP composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of greater than 50 wt %, or an amount within a range having a lower limit of 50 or 55 or 60 or 65 or 70 and an upper limit of 80 or 85 or 90, based on the combined weight of the acid copolymer and the non-acid polymer. In another particular embodiment, the relatively hard/high modulus HNP composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of less than 50 wt %, or an amount within a range having a lower limit of 10 or 15 or 20 or 25 or 30 and an upper limit of 40 or 45 or 50, based on the combined weight of the acid copolymer and the non-acid polymer

HNP compositions of the present invention, in the neat (i.e., unfilled) form, preferably have a specific gravity of from 0.95 g/cc to 0.99 g/cc. Any suitable filler, flake, fiber, particle, or the like, of an organic or inorganic material may be added to the HNP composition to increase or decrease the specific gravity, particularly to adjust the weight distribution within the golf ball, as further disclosed in U.S. Pat. Nos. 6,494,795, 6,547,677, 6,743,123, 7,074,137, and 6,688,991, the entire disclosures of which are hereby incorporated herein by reference.

In a particular embodiment, the relatively hard/high modulus HNP composition is formed by blending an acid polymer, a non-acid polymer, a cation source, and a fatty acid or metal salt thereof.

In a particular aspect of this embodiment, the acid polymer is selected from ethylene-acrylic acid and ethylene-methacrylic acid copolymers, optionally containing a softening monomer selected from n-butyl acrylate and iso-butyl acrylate. Examples of particularly suitable commercially available acid polymers include, but are not limited to, those given in Table 1 above.

In another particular aspect of this embodiment, the non-acid polymer is an elastomeric polymer. Suitable elastomeric polymers include, but are not limited to:

-   -   (a) ethylene-alkyl acrylate polymers, particularly         polyethylene-butyl acrylate, polyethylene-methyl acrylate, and         polyethylene-ethyl acrylate;     -   (b) metallocene-catalyzed polymers;     -   (c) ethylene-butyl acrylate-carbon monoxide polymers and         ethylene-vinyl acetate-carbon monoxide polymers;     -   (d) polyethylene-vinyl acetates;     -   (e) ethylene-alkyl acrylate polymers containing a cure site         monomer;     -   (f) ethylene-propylene rubbers and ethylene-propylene-diene         monomer rubbers;     -   (g) olefinic ethylene elastomers, particularly ethylene-octene         polymers, ethylene-butene polymers, ethylene-propylene polymers,         and ethylene-hexene polymers;     -   (h) styrenic block copolymers;     -   (i) polyester elastomers;     -   (j) polyamide elastomers;     -   (k) polyolefin rubbers, particularly polybutadiene,         polyisoprene, and styrene-butadiene rubber; and     -   (l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acid polymers include, but are not limited to, Lotader® ethylene-alkyl acrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, and particularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900 commercially available from Arkema Corporation; Elvaloy® AC ethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC 2116, AC3117, AC3427, and AC34035, commercially available from E. I. du Pont de Nemours and Company; Fusabond® elastomeric polymers, such as ethylene vinyl acetates, polyethylenes, metallocene-catalyzed polyethylenes, ethylene propylene rubbers, and polypropylenes, and particularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614, M603, E100, E158, E226, E265, E528, and E589, commercially available from E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenes and ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C 575, A-C 573, A-C 655, and A-C 395, commercially available from Honeywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers, and Amplify® functional polymers, and particularly Amplify® GR 207, GR 208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commercially available from The Dow Chemical Company; Enable® metallocene polyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers, and Vistalon® EPDM rubber, commercially available from ExxonMobil Chemical Company; Starflex® metallocene linear low density polyethylene, commercially available from LyondellBasell; Elvaloy® HP4051, HP441, HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers and Elvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxide polymers, commercially available from E. I. du Pont de Nemours and Company; Evatane® ethylene-vinyl acetate polymers having a vinyl acetate content of from 18 to 42%, commercially available from Arkema Corporation; Elvax® ethylene-vinyl acetate polymers having a vinyl acetate content of from 7.5 to 40%, commercially available from E. I. du Pont de Nemours and Company; Vamac® G terpolymer of ethylene, methylacrylate and a cure site monomer, commercially available from E. I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commercially available from ExxonMobil Chemical Company; Kraton® styrenic block copolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT, commercially available from Kraton Performance Polymers Inc.; Septon® styrenic block copolymers, commercially available from Kuraray Co., Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069, and 556, commercially available from E. I. du Pont de Nemours and Company; Riteflex® polyester elastomers, commercially available from Celanese Corporation; Pebax® thermoplastic polyether block amides, and particularly Pebax® 2533, 3533, 4033, and 5533, commercially available from Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify® ethylene-propylene copolymer elastomers, and Infuse® olefin block copolymers, commercially available from The Dow Chemical Company; Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO 1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially available from ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularly Royaltuf®498 maleic anhydride modified polyolefin based on an amorphous EPDM and Royaltuf®485 maleic anhydride modified polyolefin based on an semi-crystalline EPDM, commercially available from Chemtura Corporation.

Additional examples of particularly suitable commercially available elastomeric polymers include, but are not limited to, those given in Table 2 above.

The acid polymer and non-acid polymer are combined and reacted with a cation source, such that at least 80% of all acid groups present are neutralized. The present invention is not meant to be limited by a particular order for combining and reacting the acid polymer, non-acid polymer and cation source. In a particular embodiment, the fatty acid or metal salt thereof is used in an amount such that the fatty acid or metal salt thereof is present in the HNP composition in an amount of from 10 wt % to 60 wt %, or within a range having a lower limit of 10 or 20 or 30 or 40 wt % and an upper limit of 40 or 50 or 60 wt %, based on the total weight of the HNP composition. Suitable cation sources and fatty acids and metal salts thereof are further disclosed above.

In another particular aspect of this embodiment, the acid polymer is an ethylene-acrylic acid polymer having an acid content of 19 wt % or greater, the non-acid polymer is a metallocene-catalyzed ethylene-butene copolymer, optionally modified with maleic anhydride, the cation source is magnesium, and the fatty acid or metal salt thereof is magnesium oleate present in the composition in an amount of 20 to 50 wt %, based on the total weight of the composition.

The relatively hard/high modulus HNP composition optionally comprises from 0.5 wt % to 80 wt % of a plasticizer, based on the total weight of the composition. Suitable plasticizers are disclosed further below.

Plasticized Acid Copolymer Composition

Golf balls of the present invention comprise at least one layer formed from a plasticized acid copolymer composition. The plasticized acid copolymer composition is selected from (a) relatively soft/low modulus HNP compositions, as described above, additionally comprising from 0.5 wt % to 80 wt % of a plasticizer selected from the plasticizers described below, (b) relatively hard/high modulus HNP compositions, as described above, additionally comprising from 0.5 wt % to 80 wt % of a plasticizer selected from the plasticizers described below, and (c) the plasticized acid copolymer compositions described below.

Suitable plasticized acid copolymer compositions are formed by combining an acid polymer, which is optionally partially or fully neutralized, with 0.5 wt % to 80 wt % of a plasticizer, based on the total weight of the composition.

The acid copolymer of the plasticized acid copolymer composition is a copolymer of an α-olefin and a C₃-C₈ α,β-ethylenically unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates. It is understood that the acid copolymer may be a blend of two or more different acid copolymers. The α-olefin is typically present in the acid copolymer in an amount of about 15 wt % or greater, or 25 wt % or greater, or 40 wt % or greater, or 60 wt % or greater, or 75 wt % or greater, or 79 wt % or greater, or 81 wt % or greater, or 85 wt % or greater, or 90 wt % or greater, or 94 wt % or greater, or 97 wt % or greater, or 98 wt % or greater, based on the total weight of the acid copolymer. The acid is typically present in the acid copolymer in an amount of 1 or 8 or 10 or 12 or 15 or 19 or 20 or 25 or 30 or 35 or 40 wt %, based on the total weight of the acid copolymer. The α-olefin is preferably selected from ethylene and propylene. The acid is preferably selected from (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, and itaconic acid. (Meth) acrylic acid is particularly preferred. The optional softening monomer is preferably selected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.

Suitable acid copolymers are further disclosed, for example, in U.S. Pat. Nos. 6,953,820, 6,815,480, 6,762,246, 6,777,472, 6,562,906, 6,653,382, 5,691,418, and U.S. Patent Application Publication Nos. 2005/0148725, 2005/0049367, 2005/0020741, 2004/0220343, and 2003/0130434, the entire disclosures of which are hereby incorporated herein by reference.

Suitable acid copolymers also include partially and fully neutralized acid polymers, wherein the acid copolymer is reacted with a cation source, prior to and/or during the process of forming the plasticized acid copolymer composition, optionally in the presence of a high molecular weight organic acid or salt thereof, such that at least 70%, or at least 80%, or at least 90%, or at least 95%, or 100%, of all acid groups present in the plasticized acid copolymer composition are neutralized. The present invention is not meant to be limited by a particular order for combining and reacting the acid copolymer and cation source. The partially or highly neutralized acid copolymer may be diluted with a second acid copolymer to reduce the level of neutralization in the final composition.

Suitable cation sources include, but are not limited to, metal ions and compounds of alkali metals, alkaline earth metals, and transition metals; metal ions and compounds of rare earth elements; ammonium salts and monoamine salts; and combinations thereof. Preferred cation sources are metal ions and compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, tin, lithium, and rare earth metals.

Suitable high molecular weight organic acids and salts thereof are aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated monofunctional organic acids, multi-unsaturated mono-functional organic acids, dimerized derivatives thereof, the salts particularly the barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, and calcium salts thereof, and blends of two or more thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, dimerized derivatives thereof, salts thereof, and blends of two or more thereof. Suitable organic acids are more fully described, for example, in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, the organic acid or salt thereof is used in an amount such that the organic acid or salt thereof is present in the plasticized acid copolymer composition in an amount of 10 wt % or greater, or 20 wt % or greater, or 30 wt % or greater, or 40 wt % or greater, or 50 wt % or greater, or 60 wt % or greater, based on the total weight of the plasticized acid copolymer composition.

Examples of suitable commercially available acid copolymers include those given in Table 1 above. Examples of suitable commercially available partially and fully neutralized acid polymers include, but are not limited to, Surlyn® ionomers, commercially available from E. I. du Pont de Nemours and Company; AClyn® ionomers, commercially available from Honeywell International Inc.; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; and DuPont® HPF 1000, HPF 2000, HPF AD1035, and HPF AD1035 Soft, ionomeric materials commercially available from E. I. du Pont de Nemours and Company.

The plasticized acid copolymer composition comprises from 0.5 to 80 wt %, based on the total weight of the composition, of a plasticizer.

In a particular embodiment, the plasticizer is selected from N-butylbenzenesulfonamide (BBSA); N-ethylbenzenesulfonamide (EBSA); N-propylbenzenesulfonamide (PBSA); N-butyl-N-dodecylbenzenesulfonamide (BDBSA); N,N-dimethylbenzenesulfonamide (DMBSA); p-methylbenzenesulfonamide; o,p-toluene sulfonamide; p-toluene sulfonamide; 2-ethylhexyl-4-hydroxybenzoate; hexadecyl-4-hydroxybenzoate; 1-butyl-4-hydroxybenzoate; dioctyl phthalate; diisodecyl phthalate; di-(2-ethylhexyl) adipate; and tri-(2-ethylhexyl) phosphate.

In another particular embodiment, the plasticizer is selected from polytetramethylene ether glycol, e.g., PolyTHF™ 250, commercially available from BASF; propylene carbonate, e.g., Jeffsol™ PC propylene carbonate, commercially available from Huntsman Corp.; dipropyleneglycol dibenzoate, e.g., Benzoflex™ 284 plasticizer, commercially available from Eastman Chemical; and combinations of two or more thereof.

In another particular embodiment, the plasticizer is selected from benzene mono-, di-, and tricarboxylic acid esters; phthalates, such as bis(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), di-n-butyl phthalate (DnBP, DBP), butyl benzyl phthalate (BBP), diisodecyl phthalate (DIDP), dioctyl phthalate (DnOP), diisooctyl phthalate (DIOP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), and di-n-hexyl phthalate; iso- and terephthalates, such as dioctyl terephthalate and dinonyl isophthalate; trimellitates, such as trimethyl trimellitate (TMTM), tri-(2-ethylhexyl) trimellitate (TOTM), tri-(n-octyl,n-decyl) trimellitate, tri-(heptyl,nonyl) trimellitate, tri-n-octyl trimellitate; and benzoates, such as 2-ethylhexyl-4-hydroxy benzoate, n-octyl benzoate, methyl benzoate, and ethyl benzoate; and combination of two or more thereof.

In another particular embodiment, the plasticizer is selected from alkyl diacid esters commonly based on C4-C12 alkyl dicarboxylic acids, such as adipic, sebacic, azelaic, and maleic acids, e.g., bis(2-ethylhexyl)adipate (DEHA), dimethyl adipate (DMAD), monomethyl adipate (MMAD), dioctyl adipate (DOA), dibutyl sebacate (DBS), dibutyl maleate (DBM), diisobutyl maleate (DIBM), dioctyl sebacate (DOS), esters based on glycols, polyglycols and polyhydric alcohols, such as poly(ethylene glycol), mono- and di-esters, cyclohexanedimethanol esters, sorbitol derivatives, and triethylene glycol dihexanoate, diethylene glycol di-2-ethylhexanoate, tetraethylene glycol diheptanoate, and ethylene glycol dioleate.

In another particular embodiment, the plasticizer is selected from fatty acids, fatty acid salts, fatty acid amides, and fatty acid esters, including, for example, compounds such as stearic, oleic, ricinoleic, behenic, myristic, linoleic, palmitic, and lauric acid esters, salts, and mono- and bis-amides. Suitable fatty acid salts include, for example, metal stearates, erucates, laurates, oleates, palmitates, pelargonates, and the like. Also suitable are fatty alcohols and acetylated fatty alcohols, and carbonate esters, such as propylene carbonate and ethylene carbonate. Particularly suitable are, for example, alkyl oleates selected from methyl, ethyl, propyl, butyl, octyl, and decyl oleates. In a particular aspect of this embodiment, the plasticizer is selected from ethyl oleate, butyl oleate, octyl oleat, and 2-ethyl hexyl oleate. Also particularly suitable are butyl stearate, methyl acetylricinoleate, zinc oleate, ethylene bis-oleamide, stearyl erucamide, zinc stearate, calcium stearate, magnesium stearate, barium stearate.

In another particular embodiment, the plasticizer is selected from glycerol-based esters, such as soy-bean, tung, or linseed oils, and their epoxidized derivatives; polymeric polyester plasticizers formed from the esterification reaction of diacids and diglycols; and the ring-opening polymerization reaction of caprolactones with diacids or diglycols. Citrate esters and acetylated citrate esters are particularly suitable. Glycerol mono-, di-, and tri-oleates are also particularly suitable.

In another particular embodiment, the plasticizer is selected from dicarboxylic acid molecules containing both a carboxylic acid ester and a carboxylic acid salt, such as the magnesium salt of mono-methyl adipate and the zinc salt of mono-octyl glutarate; tri- and tetra-carboxylic acid esters and salts.

In another particular embodiment, the plasticizer is selected from organophosphate and organosulfur compounds, such as tricresyl phosphate (TCP), tributyl phosphate(TBP), alkyl sulfonic acid phenyl esters (ASE); sulfonamides, such as N-ethyl toluene sulfonamide, N-(2-hydroxypropyl) benzene sulfonamide, N-(n-butyl) benzene sulfonamide; and thioester and thioether variants thereof.

In another particular embodiment, the plasticizer is selected from alcohols, glycols, polyglycols, and polyethers, such as polytetramethylene ether glycol, poly(ethylene glycol), and poly(propylene glycol), oleyl alchohol, and cetyl alcohol.

In another particular embodiment, the plasticizer is selected from saturated and unsaturated, linear and cyclic, halogenated and non-halogenated hydrocarbons, and particularly mineral oils, microcrystalline waxes, and low-molecular weight polybutadiene.

In another particular embodiment, the plasticizer is selected from butylbenzenesulphonamide (BBSA), ethylhexyl para-hydroxybenzoate (EHPB) and decylhexyl para-hydroxybenzoate (DHPB), as disclosed in U.S. Pat. No. 6,376,037 to Montanari et al., the entire disclosure of which is hereby incorporated herein by reference.

In another particular embodiment, the plasticizer is selected from esters and alkylamides, such as phthalic acid esters, including, for example, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, diisononyl phthalate, ethylphthalylethyl glycolate, butylphthalylbutyl glycolate, diundecyl phthalate, and di-2-ethylhexyl tetrahydrophthalate, and those disclosed in U.S. Pat. No. 6,538,099 to Isobe et al., the entire disclosure of which is hereby incorporated herein by reference.

In another particular embodiment, the plasticizer is selected from sulphonamides such as N-butylbenzenesulphonamide, ethyltoluene-suiphonamide, N-cyclohexyltoluenesulphonamide, 2-ethylhexyl-para-hydroxybenzoate, 2-decylhexyl-para-hydroxybenzoate, oligoethyleneoxytetrahydrofurfuryl alcohol, and oligoethyleneoxy malonate; esters of hydroxybenzoic acid; esters and ethers of tetrahydrofurfuryl alcohol, and esters of citric acid or hydroxymalonic acid; and those disclosed in U.S. Pat. No. 7,045,185 to Jacques et al, the entire disclosure of which is hereby incorporated herein by reference.

In another particular embodiment, the plasticizer is selected from sulfonamides, such as N-alkyl benzenesulfonamides and toluenesufonamides, and particularly N-butylbenzenesulfonamide, N-(2-hydroxypropyl)benzenesulfonamide, N-ethyl-o-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfonamide, and the sulfonamides disclosed in U.S. Pat. No. 7,297,737 to Fish, Jr. et al., and U.S. Patent Application Publication No. 2010/0183837 to Hochstetter et al., the entire disclosures of which are hereby incorporated herein by reference.

The plasticizer is preferably present in the plasticized acid copolymer composition in an amount sufficient to substantially change the stiffness and/or hardness of the acid copolymer. In a particular embodiment, the plasticizer is present in an amount of 0.5% or 1% or 3% or 5% or 7% or 8% or 9% or 10% or 12% or 15% or 18% or 20% or 22% or 25% or 30% or 35% or 40% or 42% or 50% or 55% or 60% or 66% or 71% or 75% or 80%, by weight based on the total weight of the plasticized acid copolymer composition, or the plasticizer is present in an amount within a range having a lower limit and an upper limit selected from these values.

In a particular embodiment, a non-plasticized composition comprising an ethylene acid copolymer has a first flexural modulus value, a plasticized composition consisting of the non-plasticized composition and from 0.5 wt % to 80 wt % of a plasticizer has a second flexural modulus value, wherein the second flexural modulus value is at least 1% less; or at least 2% less; or at least 4% less; or at least 8% less; or at least 10% less than the first flexural modulus value. In a particular aspect of this embodiment, the plasticized composition has a flexural modulus of about 500 psi (or less), or a flexural modulus of 1,000 psi or 1,600 psi or 2,000 psi or 4,200 psi or 7,500 psi or 9,000 psi or 10,000 psi or 20,000 psi or 40,000 psi or 50,000 psi or 60,000 psi or 70,000 psi or 80,000 psi or 90,000 psi or 100,000 psi or 110,000 psi or 120,000 psi or 130,000 psi or 140,000 psi or 160,000 psi or 180,000 psi or 200,000 psi or 300,000 psi, or a flexural modulus within a range having a lower limit and an upper limit selected from these values.

In another particular embodiment, a non-plasticized composition comprising an ethylene acid copolymer has a first Tg value, a plasticized composition consisting of the non-plasticized composition and from 0.5 wt % to 80 wt % of a plasticizer has a second Tg value, wherein the second Tg value is at least 1° less, or at least 2° less, or at least 4° less, or at least 8° less, or at least 10° less than the first Tg value, or the second Tg value is within 1° of the first Tg value.

In another particular embodiment, a non-plasticized composition comprising an ethylene acid copolymer has a first compression, a plasticized composition consisting of the non-plasticized composition and from 0.5 wt % to 80 wt % of a plasticizer has a second compression, wherein the second compression is equal to or less than the first compression.

In a particular embodiment, the plasticized acid copolymer composition has a Shore D hardness of 5 or 8 or 10 or 12 or 14 or 28 or 30 or 32 or 34 or 35 or 38 or 40, or a Shore D hardness within a range having a lower limit and an upper limit of these values.

In another particular embodiment, the plasticized acid copolymer composition has a Shore C hardness of 10 or 13 or 15 or 17 or 19 or 44 or 46 or 48 or 50 or 53 or 55, or a Shore C hardness within a range having a lower limit and an upper limit of these values.

In another particular embodiment, the plasticized acid copolymer composition has a Shore D hardness of 25 or 28 or 30 or 32 or 35 or 36 or 38 or 40 or 42 or 45 or 48 or 50 or 54 or 56 or 60, or a Shore D hardness within a range having a lower limit and an upper limit of these values.

In another particular embodiment, the plasticized acid copolymer composition has a Shore C hardness of 30 or 33 or 35 or 37 or 39 or 41 or 43 or 62 or 64 or 66 or 68 or 71 or 73 or 75, or a Shore C hardness within a range having a lower limit and an upper limit of these values.

In another particular embodiment, the plasticized acid copolymer composition has a Shore D hardness of 42 or 44 or 47 or 51 or 53 or 58 or 60 or 65 or 72 or 77 or 80 or 84 or 91 or 95, or a Shore D hardness within a range having a lower limit and an upper limit of these values.

In another particular embodiment, the plasticized acid copolymer composition has a Shore C hardness of 57 or 59 or 62 or 66 or 72 or 75 or 78 or 84 or 87 or 90 or 93 or 95 or 97 or 99, or a Shore C hardness within a range having a lower limit and an upper limit of these values.

Plasticized acid copolymer compositions of the present invention are not limited by any particular method or any particular equipment for making the compositions. In a particular embodiment, the composition is prepared by the following process. The acid copolymer, which is optionally already partially or fully neutralized, plasticizer, and optionally one or more of: non-acid polymer, melt-flow modifier, and additive/filler are simultaneously or individually fed into a melt extruder, such as a single or twin screw extruder. If the level of neutralization of the acid polymer is to be increased, a suitable amount of cation source is added to achieve the desired level of neutralization. The components are intensively mixed prior to being extruded as a strand from the die-head. Methods for incorporating plasticizer into the thermoplastic compositions described herein are further disclosed in co-pending U.S. patent application Ser. No. 13/929,841, and in U.S. Pat. Nos. 8,523,708 and 8,523,709, the entire disclosures of which are hereby incorporated herein by reference.

In a particular embodiment, the plasticized acid copolymer composition is formed by blending an acid polymer, a non-acid polymer, a cation source, and a high molecular weight organic acid or salt thereof, and combining the resulting composition with a plasticizer. For purposes of the present invention, maleic anhydride modified polymers are defined herein as a non-acid polymer despite having anhydride groups that can ring-open to the acid form during processing of the polymer to form the HNP compositions herein. The maleic anhydride groups are grafted onto a polymer, are present at relatively very low levels, and are not part of the polymer backbone, as is the case with the acid copolymers.

Suitable non-acid polymer(s) are preferably selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, chlorinated polyethylene, polyvinyl chloride, chlorinated polyvinyl chloride, and functionalized derivatives thereof.

In a particular embodiment, the non-acid polymer is an elastomeric polymer selected from the group consisting of:

-   -   (a) ethylene-alkyl acrylate polymers, particularly         polyethylene-butyl acrylate, polyethylene-methyl acrylate, and         polyethylene-ethyl acrylate;     -   (b) metallocene-catalyzed polymers;     -   (c) ethylene-butyl acrylate-carbon monoxide polymers and         ethylene-vinyl acetate-carbon monoxide polymers;     -   (d) polyethylene-vinyl acetates;     -   (e) ethylene-alkyl acrylate polymers containing a cure site         monomer;     -   (f) ethylene-propylene rubbers and ethylene-propylene-diene         monomer rubbers;     -   (g) olefinic ethylene elastomers, particularly ethylene-octene         polymers, ethylene-butene polymers, ethylene-propylene polymers,         and ethylene-hexene polymers;     -   (h) styrenic block copolymers;     -   (i) polyester elastomers;     -   (j) polyamide elastomers;     -   (k) polyol efin rubbers, particularly polybutadiene,         polyisoprene, and styrene-butadiene rubber; and     -   (l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acid polymers include, but are not limited to, Lotader® ethylene-alkyl acrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, and particularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900 commercially available from Arkema Corporation; Elvaloy® AC ethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC 2116, AC3117, AC3427, and AC34035, commercially available from E. I. du Pont de Nemours and Company; Fusabond® elastomeric polymers, such as ethylene vinyl acetates, polyethylenes, metallocene-catalyzed polyethylenes, ethylene propylene rubbers, and polypropylenes, and particularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614, M603, E100, E158, E226, E265, E528, and E589, commercially available from E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenes and ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C 575, A-C 573, A-C 655, and A-C 395, commercially available from Honeywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers, and Amplify® functional polymers, and particularly Amplify® GR 207, GR 208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commercially available from The Dow Chemical Company; Enable® metallocene polyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers, and Vistalon® EPDM rubber, commercially available from ExxonMobil Chemical Company; Starflex® metallocene linear low density polyethylene, commercially available from LyondellBasell; Elvaloy® HP4051, HP441, HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers and Elvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxide polymers, commercially available from E. I. du Pont de Nemours and Company; Evatane® ethylene-vinyl acetate polymers having a vinyl acetate content of from 18 to 42%, commercially available from Arkema Corporation; Elvax® ethylene-vinyl acetate polymers having a vinyl acetate content of from 7.5 to 40%, commercially available from E. I. du Pont de Nemours and Company; Vamac® G terpolymer of ethylene, methylacrylate and a cure site monomer, commercially available from E. I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commercially available from ExxonMobil Chemical Company; Kraton® styrenic block copolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT, commercially available from Kraton Performance Polymers Inc.; Septon® styrenic block copolymers, commercially available from Kuraray Co., Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069, and 556, commercially available from E. I. du Pont de Nemours and Company; Riteflex® polyester elastomers, commercially available from Celanese Corporation; Pebax® thermoplastic polyether block amides, and particularly Pebax® 2533, 3533, 4033, and 5533, commercially available from Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify® ethylene-propylene copolymer elastomers, and Infuse® olefin block copolymers, commercially available from The Dow Chemical Company; Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO 1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially available from ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularly Royaltuf®498 maleic anhydride modified polyolefin based on an amorphous EPDM and Royaltuf®485 maleic anhydride modified polyolefin based on an semi-crystalline EPDM, commercially available from Chemtura Corporation.

Additional examples of particularly suitable commercially available elastomeric non-acid polymers include, but are not limited to, those given in Table 2 above.

In a particular embodiment, the plasticized acid copolymer composition is formed by blending an ethylene-acrylic acid polymer, a metallocene-catalyzed ethylene-butene copolymer optionally modified with maleic anhydride, a magnesium cation source, and 20 to 50 wt % magnesium oleate, and combining the resulting composition with a plasticizer selected from the plasticizers described above.

In another particular embodiment, the plasticized acid copolymer composition is formed by blending a highly neutralized polymer, such as DuPont HPF 2000 with 10 to 40 wt % of a fatty acid ester, such as ethyl oleate or butyl oleate.

Plasticized acid copolymer compositions of the present invention optionally include additives(s) and/or filler(s), such as chemical blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nano-fillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, TiO₂, acid copolymer wax, surfactants, and fillers, such as zinc oxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc carbonate, barium carbonate, clay, tungsten, tungsten carbide, silica, lead silicate, regrind (recycled material), and mixtures thereof.

Golf Ball Applications

Golf balls of the present invention comprise at least one layer formed from a relatively soft HNP composition and at least one layer formed from a relatively hard HNP composition, or at least one layer formed from a relatively low modulus HNP composition and at least one layer formed from a relatively high modulus HNP composition.

In one embodiment, the present invention provides a golf ball having a multi-layer core and a cover, wherein the core includes a layer formed from a relatively soft HNP composition and a layer formed from a relatively hard HNP composition. In a particular aspect of this embodiment, the relatively soft HNP composition is plasticized. In another particular aspect of this embodiment, the relatively hard HNP composition is plasticized. In another particular aspect of this embodiment, the relatively soft HNP composition and the relatively hard HNP composition are plasticized.

In another embodiment, the present invention provides a golf ball having a dual-layer core and a cover, wherein the dual-layer core includes a layer formed from a low modulus HNP composition and a layer formed from a high modulus HNP composition. In a particular aspect of this embodiment, the relatively low modulus HNP composition is plasticized. In another particular aspect of this embodiment, the relatively high modulus HNP composition is plasticized. In another particular aspect of this embodiment, the relatively low modulus HNP composition and the relatively high modulus HNP composition are plasticized.

Optionally, the soft (or low modulus HNP composition) and/or the hard (or high modulus) HNP composition is replaced with a different plasticized acid copolymer composition. Thus, in one embodiment, the golf ball includes a layer formed from a soft (or low modulus) HNP composition and a plasticized acid copolymer composition, and, in another embodiment, the golf ball includes a layer formed from a hard (or high modulus) HNP composition and a plasticized acid copolymer composition.

In the embodiments disclosed herein, the relatively soft/low modulus HNP composition and/or the relatively hard/high modulus HNP composition and/or the plasticized acid copolymer composition can be either foamed or filled with density adjusting materials to provide desirable golf ball performance characteristics.

Golf balls having a layer formed from a relatively soft HNP composition and a layer formed from a relatively hard HNP composition are further disclosed, for example, in U.S. Patent Application Publication No. 2007/0207880, the entire disclosure of which is hereby incorporated herein by reference.

Golf balls having a layer formed from a low modulus HNP composition and a layer formed from a high modulus HNP composition are further disclosed, for example, in U.S. Pat. No. 7,211,008, the entire disclosure of which is hereby incorporated herein by reference.

In one embodiment, the present invention provides a golf ball having a multi-layer core, wherein the core comprises a center, an outer core layer, and an intermediate core layer disposed between the center and the outer core layer. Each one of the core layers, including the center, may be formed from a composition disclosed herein or a blend of compositions disclosed herein, so long as at least one layer is formed from a relatively soft (or low modulus) HNP composition and at least one layer is formed from a relatively hard (or high modulus) HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized, or, alternatively, at least one layer is formed from a soft HNP composition or hard HNP composition and at least one layer is formed from a plasticized acid copolymer composition. The multi-layer core optionally comprises two or more layers formed from the same or different relatively soft HNP compositions and/or two or more layers formed from the same or different relatively hard HNP compositions and/or two or more layers formed from the same or different plasticized acid copolymer compositions.

In a particular aspect of this embodiment, the intermediate core layer is formed from a relatively hard HNP composition and the outer core layer is formed from a relatively soft HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the intermediate core layer is formed from a relatively soft HNP composition and the outer core layer is formed from a relatively hard HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the intermediate core layer is formed from a relatively hard HNP composition, which is optionally plasticized, and the outer core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the intermediate core layer is formed from a relatively soft HNP composition, which is optionally plasticized, and the outer core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the intermediate core layer is formed from a plasticized acid copolymer composition and the outer core layer is formed from a relatively hard HNP composition, which is optionally plasticized.

In another particular aspect of this embodiment, the intermediate core layer is formed from a plasticized acid copolymer composition and the outer core layer is formed from a relatively soft HNP composition, which is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively soft HNP composition and the intermediate core layer is formed from a relatively hard HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition and the intermediate core layer is formed from a relatively soft HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition, which is optionally plasticized, and the intermediate core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the center is formed from a relatively soft HNP composition, which is optionally plasticized, and the intermediate core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the center is formed from a plasticized acid copolymer composition and the intermediate core layer is formed from a relatively hard HNP composition, which is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a plasticized acid copolymer composition and the intermediate core layer is formed from a relatively soft HNP composition, which is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively soft HNP composition and the outer core layer is formed from a relatively hard HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition and the outer core layer is formed from a relatively soft HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition, which is optionally plasticized, and the outer core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the center is formed from a relatively soft HNP composition, which is optionally plasticized, and the outer core layer is formed from a plasticized acid copolymer composition.

In another particular aspect of this embodiment, the center is formed from a plasticized acid copolymer composition and the outer core layer is formed from a relatively hard HNP composition, which is optionally plasticized.

In another particular aspect of this embodiment, the center is formed from a plasticized acid copolymer composition and the outer core layer is formed from a relatively soft HNP composition, which is optionally plasticized.

In another embodiment, the present invention provides a golf ball having a dual-layer core, wherein the core includes a center and an outer core layer. In a particular aspect of this embodiment, the center is formed from a low modulus HNP composition and the outer core layer is formed from a high modulus HNP composition, wherein at least one of the low modulus or high modulus HNP compositions is optionally plasticized. In another particular aspect of this embodiment, the center is formed from a high modulus HNP composition and the outer core layer is formed from a low modulus HNP composition, wherein at least one of the low modulus or high modulus HNP compositions is optionally plasticized.

In another embodiment, the present invention provides a golf ball having a dual- or multi-layer core, wherein the core includes a center and an outer core layer. In a particular aspect of this embodiment, the center is formed from a relatively soft HNP composition and the outer core layer is formed from a relatively hard HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized. In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition and the outer core layer is formed from a relatively soft HNP composition, wherein at least one of the relatively soft or relatively hard HNP compositions is optionally plasticized. In another particular aspect of this embodiment, the center is formed from a relatively soft HNP composition and the outer core layer is formed from an acid copolymer composition, at least one of which is plasticized. In another particular aspect of this embodiment, the center is formed from a relatively hard HNP composition and the outer core layer is formed from an acid copolymer composition, at least one of which is plasticized. In another particular aspect of this embodiment, the center is formed from an acid copolymer composition and the outer core layer is formed from a relatively soft HNP composition, at least one of which is plasticized. In another particular aspect of this embodiment, the center is formed from an acid copolymer composition and the outer core layer is formed from a relatively hard HNP composition, at least one of which is plasticized. In a further aspect of these particular embodiments, the core optionally includes an intermediate core layer formed from a rubber composition, and/or the ball optionally includes a rubber intermediate layer disposed between the core and the cover.

In embodiments of the present invention wherein the core includes a layer formed from a composition other than a relatively soft HNP composition or a relatively hard HNP composition, such layer may be formed from any suitable golf ball composition. Preferably, the layer that is not formed from a relatively soft HNP composition or a relatively hard HNP composition is formed from a rubber composition or from a highly resilient thermoplastic polymer such as a conventional HNP composition. Particularly suitable thermoplastic polymers include Surlyn® ionomers, Hytrel® thermoplastic polyester elastomers, and ionomeric materials sold under the trade names DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, all of which are commercially available from E. I. du Pont de Nemours and Company; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; and Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc. Suitable rubber and thermoplastic polymer compositions are further disclosed below.

In one embodiment, the present invention is directed to a golf ball comprising a center, an outer core layer, an intermediate core layer disposed between the center and the outer core layer, and one or more cover layers. In a particular aspect of this embodiment, the golf ball has one or more of the following properties:

-   -   (a) a center having a diameter within a range having a lower         limit of 0.250 or 0.500 or 0.600 or 0.750 or 0.800 or 1.000 or         1.100 or 1.200 inches and an upper limit of 1.300 or 1.350 or         1.400 or 1.500 or 1.510 or 1.530 or 1.550 or 1.570 or 1.580 or         1.600 inches;     -   (b) an intermediate core layer having a thickness within a range         having a lower limit of 0.020 or 0.025 or 0.032 or 0.050 or         0.075 or 0.100 or 0.125 inches and an upper limit of 0.150 or         0.175 or 0.200 or 0.220 or 0.250 or 0.280 or 0.300 inches;     -   (c) an outer core layer having a thickness within a range having         a lower limit of 0.010 or 0.020 or 0.025 or 0.030 or 0.032         inches and an upper limit of 0.070 or 0.080 or 0.100 or 0.150 or         0.310 or 0.440 or 0.560 inches;     -   (d) an intermediate core layer and an outer core layer having a         combined thickness within a range having a lower limit of 0.040         inches and an upper limit of 0.560 or 0.800 inches;     -   (e) an outer core layer having a thickness such that a golf ball         subassembly including the center, intermediate core layer, and         core layer has an outer diameter within a range having a lower         limit of 1.000 or 1.300 or 1.400 or 1.450 or 1.500 or 1.510 or         1.530 or 1.550 inches and an upper limit of 1.560 or 1.570 or         1.580 or 1.590 or 1.600 or 1.620 or 1.640 inches;     -   (f) a center having a surface hardness of 65 Shore C or greater,         or 70 Shore C or greater, or a surface hardness within a range         having a lower limit of 55 or 60 or 65 or 70 or 75 Shore C and         an upper limit of 80 or 85 Shore C;     -   (g) a center having a center hardness (H) within a range having         a lower limit of 20 or 25 or 30 or 35 or 45 or 50 or 55 Shore C         and an upper limit of 60 or 65 or 70 or 75 or 90 Shore C; an         outer core layer having a surface hardness (S) within a range         having a lower limit of 20 or 25 or 30 or 35 or 45 or 55 Shore C         and an upper limit of 60 or 70 or 75 or 90 Shore C; and         -   (i) H=S;         -   (ii) H<S, and the difference between H and S is from −15 to             40, preferably from −15 to 22, more preferably from −10 to             15, and even more preferably from −5 to 10; or         -   (iii) S<H, and the difference between H and S is from −15 to             40, preferably from −15 to 22, more preferably from −10 to             15, and even more preferably from −5 to 10;     -   (h) an intermediate layer having a surface hardness (I) that is         greater than both the center hardness of the center (H) and the         surface hardness of the outer core layer (S); I is preferably 40         Shore C or greater or within a range having an lower limit of 40         or 45 or 50 or 85 Shore C and an upper limit of 90 or 93 or 95         Shore C; the Shore D range for I is preferably from 40 to 80,         more preferably from 50 to 70;     -   (i) each core layer having a specific gravity of from 0.50 g/cc         to 5.00 g/cc; preferably from 1.05 g/cc to 1.25 g/cc; more         preferably from 1.10 g/cc to 1.18 g/cc;     -   (j) a center having a surface hardness greater than or equal to         the center hardness of the center;     -   (k) a center having a positive hardness gradient wherein the         surface hardness of the center is at least 10 Shore C units         greater than the center hardness of the center;     -   (l) an outer core layer having a surface hardness greater than         or equal to the surface hardness and center hardness of the         center;     -   (m) a center having a compression of 40 or less;     -   (n) a center having a compression of from 20 to 40; and     -   (o) a golf ball subassembly including the center and the         intermediate core layer has a compression of 30 or greater, or         40 or greater, or 50 or greater, or 60 or greater, or a         compression within a range having a lower limit of 30 or 40 or         50 or 60 and an upper limit of 65 or 75 or 85 or 95 or 105.

In another embodiment, the present invention is directed to a golf ball comprising a center, an outer core layer, an intermediate core layer disposed between the center and the outer core layer, and one or more cover layers, wherein the golf ball has one or more of the following properties:

-   -   (a) a center having a diameter within a range having a lower         limit of 0.100 or 0.125 or 0.250 inches and an upper limit of         0.375 or 0.500 or 0.750 or 1.000 inches;     -   (b) an intermediate core layer having a thickness within a range         having a lower limit of 0.050 or 0.075 or 0.100 or 0.125 or         0.150 or 0.200 inches and an upper limit of 0.300 or 0.350 or         0.400 or 0.500 inches;     -   (c) an outer core layer having a thickness within a range having         a lower limit of 0.010 or 0.020 or 0.025 or 0.030 or 0.032         inches and an upper limit of 0.070 or 0.080 or 0.100 or 0.150 or         0.310 or 0.440 or 0.560 inches;     -   (d) an outer core layer having a thickness such that a golf ball         subassembly including the center, intermediate core layer, and         core layer has an outer diameter within a range having a lower         limit of 1.000 or 1.300 or 1.400 or 1.450 or 1.500 or 1.510 or         1.530 or 1.550 inches and an upper limit of 1.560 or 1.570 or         1.580 or 1.590 or 1.600 or 1.620 or 1.640 or 1.660 inches;     -   (e) a center having a surface hardness of 65 Shore C or greater,         or 70 Shore C or greater, or greater than 70 Shore C, or 80         Shore C or greater, or a surface hardness within a range having         a lower limit of 70 or 75 or 80 Shore C and an upper limit of 90         or 95 Shore C;     -   (f) an outer core layer having a surface hardness less than or         equal to the surface hardness of the center;     -   (g) an outer core having a surface hardness of 65 Shore C or         greater, or 70 Shore C or greater, or greater than 70 Shore C,         or 80 Shore C or greater, or 85 Shore C or greater;     -   (h) an intermediate core layer having a surface hardness that is         less than both the surface hardness of the center and the         surface hardness of the outer core layer;     -   (i) an intermediate core layer having a surface hardness of less         than 80 Shore C, or less than 70 Shore C, or less than 60 Shore         C;     -   (j) a center specific gravity less than or equal to or         substantially the same as (i.e., within 0.1 g/cc) the outer core         layer specific gravity;     -   (j) a center specific gravity within a range having a lower         limit of 0.50 or 0.90 or 1.05 or 1.13 g/cc and an upper limit of         1.15 or 1.18 or 1.20 g/cc;     -   (k) an outer core layer specific gravity of 1.00 g/cc or         greater, or 1.05 g/cc or greater, or 1.10 g/cc or greater;     -   (l) an intermediate core layer specific gravity of 1.00 g/cc or         greater, or 1.05 g/cc or greater, or 1.10 g/cc or greater;     -   (m) an intermediate core layer specific gravity substantially         the same as (i.e., within 0.1 g/cc) the outer core layer         specific gravity;     -   (n) a center having a surface hardness greater than or equal to         the center hardness of the center;     -   (o) a center having a positive hardness gradient wherein the         surface hardness of the center is at least 10 Shore C units         greater than the center hardness of the center;     -   (p) a center having a compression of 40 or less;     -   (q) a center having a compression of from 20 to 40; and     -   (r) a golf ball subassembly including the center and the         intermediate core layer has a compression of 30 or greater, or         40 or greater, or 50 or greater, or 60 or greater, or a         compression within a range having a lower limit of 30 or 40 or         50 or 60 or 65 and an upper limit of 70 or 75 or 85 or 90 or 95         or 105.

In another embodiment, the present invention is directed to a golf ball comprising a center, an outer core layer, and one or more cover layers. In a particular aspect of this embodiment, the golf ball has one or more of the following properties:

-   -   (a) a center having a diameter within a range having a lower         limit of 0.500 or 0.750 or 1.000 or 1.100 or 1.200 inches and an         upper limit of 1.300 or 1.350 or 1.400 or 1.550 or 1.570 or         1.580 inches;     -   (b) a center having a diameter within a range having a lower         limit of 0.750 or 0.850 or 0.875 inches and an upper limit of         1.125 or 1.150 or 1.190 inches;     -   (c) an outer core layer enclosing the center such that the         dual-layer core has an overall diameter within a range having a         lower limit of 1.400 or 1.500 or 1.510 or 1.520 or 1.525 inches         and an upper limit of 1.540 or 1.550 or 1.555 or 1.560 or 1.590         inches, or an outer core layer having a thickness within a range         having a lower limit of 0.020 or 0.025 or 0.032 inches and an         upper limit of 0.310 or 0.440 or 0.560 inches;     -   (d) a center having a center hardness of 50 Shore C or greater,         or 55 Shore C or greater, or 60 Shore C or greater, or a center         hardness within a range having a lower limit of 50 or 55 or 60         Shore C and an upper limit of 65 or 70 or 80 Shore C;     -   (e) a center having a surface hardness of 65 Shore C or greater,         or 70 Shore C or greater, or 75 Shore C or greater, or a surface         hardness within a range having a lower limit of 55 or 60 or 65         or 70 or 75 Shore C and an upper limit of 80 or 85 or 90 or 95         Shore C;     -   (f) an outer core layer having a surface hardness of 50 Shore C         or greater, or 55 Shore C or greater, or 75 Shore C or greater,         or 80 Shore C or greater, or greater than 80 Shore C, or 85         Shore C or greater, or greater than 85 Shore C, or 87 Shore C or         greater, or greater than 87 Shore C, or 89 Shore C or greater,         or greater than 89 Shore C, or 90 Shore C or greater, or greater         than 90 Shore C, or a surface hardness within a range having a         lower limit of 50 or 75 or 80 or 85 Shore C and an upper limit         of 80 or 85 or 90 or 95 Shore C;     -   (g) a center having a surface hardness greater than or equal to         the center hardness of the center;     -   (h) a center having a positive hardness gradient wherein the         surface hardness of the center is at least 10 Shore C units         greater than the center hardness of the center;     -   (i) an outer core layer having a surface hardness greater than         or equal to the surface hardness and center hardness of the         center;     -   (j) an outer core layer having a surface hardness less than the         surface hardness of the center;     -   (k) a core having a positive hardness gradient wherein the         surface hardness of the outer core layer is at least 20 Shore C         units greater, or at least 25 Shore C units greater, or at least         30 Shore C units greater, than the center hardness of the         center;     -   (l) a center having a compression of 40 or less; and     -   (m) a center having a compression of from 20 to 40.

In another particular embodiment, the present invention is directed to a golf ball comprising a core and a cover, wherein the core comprises a layer formed from a first composition comprising an acid copolymer and a layer formed from a second composition comprising an acid copolymer. The first composition and second composition are selected from the relatively soft/low modulus HNP compositions, the relatively hard/high modulus HNP compositions, and the plasticized acid copolymer compositions disclosed herein. In a particular aspect of this embodiment, the golf ball has one or more of the following properties:

-   -   (a) a center having a diameter of 0.50 inches or 0.75 inches or         1.00 inches, or 1.25 inches or 1.30 inches, or a diameter within         a range having a lower limit and an upper limit selected from         these values;     -   (b) a center hardness of 50 Shore C or greater, and an outer         core layer surface hardness of 75 Shore C or greater, wherein         the outer core layer surface hardness is optionally greater than         the center hardness;     -   (c) a center hardness of 75 Shore C or greater, and an outer         core layer surface hardness of 50 Shore C or greater, wherein         the outer core layer surface hardness is optionally less than         the center hardness;     -   (d) an inner cover layer having a material hardness less than         the surface hardness of the outer core layer; and     -   (e) at least one of the first composition and the second         composition is at least partially neutralized such that at least         70% of all acid groups present in the composition are         neutralized;     -   (f) at least one of the first composition and the second         composition comprises from 0.5 wt % to 80 wt %, based on the         total weight of the composition, of a plasticizer, wherein the         plasticizer is optionally a fatty acid ester;     -   (g) an additional core layer formed from a rubber composition,         wherein the rubber composition is optionally selected from         polybutadiene and thermosetting polyurethane;     -   (h) an additional core layer formed from a thermoplastic         elastomer composition selected from styrenic block copolymers,         polyolefin blends, elastomeric alloys, thermoplastic         polyurethanes, thermoplastic polyesters, and thermoplastic         polyamides (e.g., Hytrel® thermoplastic polyester elastomers,         commercially available from E. I. du Pont de Nemours and         Company; Kraton® styrenic block copolymers, commercially         available from Kraton Performance Polymers Inc.; Septon®         styrenic block copolymers, commercially available from Kuraray         Co., Ltd.; Riteflex® polyester elastomers, commercially         available from Celanese Corporation; Pelprene® polyester         elastomers, commercially available from Toyobo Co., Ltd.; Pebax®         thermoplastic polyether block amides, commercially available         from Arkema Inc.; and blends of two or more thereof);     -   (i) the core comprises a center formed from the first         composition and an outer core layer formed from the second         composition, wherein the acid copolymer of the first composition         is a relatively soft (or low modulus) HNP, the acid copolymer of         the second composition is a relatively hard (or high modulus)         HNP, and the modulus of the first acid copolymer is at least         10%, or at least 20%, or at least 25% or at least 30%, or at         least 35% less than the modulus of the second acid copolymer;         and     -   (j) the core comprises a center formed from the first         composition and an outer core layer formed from the second         composition, wherein the acid copolymer of the first composition         is a relatively hard (or high modulus) HNP, the acid copolymer         of the second composition is a relatively soft (or low modulus)         HNP, and the modulus of the second acid copolymer is at least         10%, or at least 20%, or at least 25% or at least 30%, or at         least 35% less than the modulus of the first acid copolymer.         The weight distribution of cores disclosed herein can be varied         to achieve certain desired parameters, such as spin rate,         compression, and initial velocity.

Golf ball cores of the present invention typically have an overall core compression of less than 100, or a compression of 87 or less, or an overall core compression within a range having a lower limit of 20 or 50 or 60 or 65 or 70 or 75 and an upper limit of 80 or 85 or 90 or 100 or 110 or 120, or an overall core compression of about 80. Compression is an important factor in golf ball design. For example, the compression of the core can affect the ball's spin rate off the driver and the feel. As disclosed in Jeff Dalton's Compression by Any Other Name, Science and Golf IV Proceedings of the World Scientific Congress of Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), several different methods can be used to measure compression, including Atti compression, Riehle compression, load/deflection measurements at a variety of fixed loads and offsets, and effective modulus. For purposes of the present invention, “compression” refers to Atti compression and is measured according to a known procedure, using an Atti compression test device, wherein a piston is used to compress a ball against a spring. The travel of the piston is fixed and the deflection of the spring is measured. The measurement of the deflection of the spring does not begin with its contact with the ball; rather, there is an offset of approximately the first 1.25 mm (0.05 inches) of the spring's deflection. Very low stiffness cores will not cause the spring to deflect by more than 1.25 mm and therefore have a zero compression measurement. The Atti compression tester is designed to measure objects having a diameter of 42.7 mm (1.68 inches); thus, smaller objects, such as golf ball cores, must be shimmed to a total height of 42.7 mm to obtain an accurate reading. Conversion from Atti compression to Riehle (cores), Riehle (balls), 100 kg deflection, 130-10 kg deflection or effective modulus can be carried out according to the formulas given in J. Dalton.

Golf ball cores of the present invention typically have a coefficient of restitution (“COR”) at 125 ft/s of at least 0.75, preferably at least 0.78, and more preferably at least 0.79. COR, as used herein, is determined according to a known procedure wherein a golf ball or golf ball subassembly (e.g., a golf ball core) is fired from an air cannon at a given velocity (125 ft/s for purposes of the present invention). Ballistic light screens are located between the air cannon and the steel plate to measure ball velocity. As the ball travels toward the steel plate, it activates each light screen, and the time at each light screen is measured. This provides an incoming transit time period proportional to the ball's incoming velocity. The ball impacts the steel plate and rebounds though the light screens, which again measure the time period required to transit between the light screens. This provides an outgoing transit time period proportional to the ball's outgoing velocity. COR is then calculated as the ratio of the outgoing transit time period to the incoming transit time period, COR=T_(out)/T_(in).

Cores of the present invention are enclosed with a cover, which may be a single-, dual-, or multi-layer cover.

Suitable cover layer materials for the golf balls disclosed herein include, but are not limited to, ionomer resin and blends thereof (particularly Surlyn® ionomer resin), polyurethanes, polyureas, (meth)acrylic acid, thermoplastic rubber polymers, polyethylene, and synthetic or natural vulcanized rubber, such as balata. Suitable commercially available ionomeric cover materials include, but are not limited to, Surlyn® ionomer resins and DuPont® HPF 1000, HPF 2000, HPF AD 1035, HPF AD 1040, commercially available from E. I. du Pont de Nemours and Company; and Iotek® ionomers, commercially available from ExxonMobil Chemical Company.

Particularly suitable outer cover layer materials include relatively soft polyurethanes and polyureas. When used as cover layer materials, polyurethanes and polyureas can be thermoset or thermoplastic. Thermoset materials can be formed into golf ball layers by conventional casting or reaction injection molding techniques. Thermoplastic materials can be formed into golf ball layers by conventional compression or injection molding techniques. Light stable polyureas and polyurethanes are preferred for the outer cover layer material. Additional suitable cover and rubber core materials are disclosed, for example, in U.S. Patent Application Publication No. 2005/0164810, U.S. Pat. No. 5,919,100, and PCT Publications WO00/23519 and WO00/29129, the entire disclosures of which are hereby incorporated herein by reference. In embodiments of the present invention wherein a golf ball having a single layer cover is provided, the cover layer material is preferably selected from polyurethane and polyurea. In embodiments of the present invention wherein a golf ball having a dual cover is provided, the inner cover layer is preferably a high modulus thermoplastic, and the outer cover layer is preferably selected from polyurethane and polyurea.

Suitable cover layer materials also include blends of ionomers with thermoplastic elastomers. Suitable ionomeric cover materials are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated by reference. Suitable polyurethane cover materials are further disclosed in U.S. Pat. Nos. 5,334,673, 6,506,851, 6,756,436, and 7,105,623, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyurea cover materials are further disclosed in U.S. Pat. Nos. 5,484,870 and 6,835,794, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyurethane-urea hybrids are blends or copolymers comprising urethane or urea segments as disclosed in U.S. Patent Application Publication No. 2007/0117923, the entire disclosure of which is hereby incorporated herein by reference. Additional suitable cover materials are disclosed, for example, in U.S. Patent Application Publication No. 2005/0164810, U.S. Pat. No. 5,919,100, and PCT Publications WO00/23519 and WO00/29129, the entire disclosures of which are hereby incorporated herein by reference.

The ionomeric composition of the inner cover layer is preferably selected from:

-   -   (a) a composition comprising a “high acid ionomer” (i.e., having         an acid content of greater than 16 wt %), such as Surlyn 8150®,         a copolymer of ethylene and methacrylic acid, having an acid         content of 19 wt %, which is 45% neutralized with sodium,         commercially available from E. I. du Pont de Nemours and         Company;     -   (b) a composition comprising a high acid ionomer and a maleic         anhydride-grafted non-ionomeric polymer (e.g., Fusabond 572D®, a         maleic anhydride-grafted, metallocene-catalyzed ethylene-butene         copolymer having about 0.9 wt % maleic anhydride grafted onto         the copolymer, commercially available from E. I. du Pont de         Nemours and Company). A particularly preferred blend of high         acid ionomer and maleic anhydride-grafted polymer is a 84 wt         %/16 wt % blend of Surlyn 8150® and Fusabond 572D®. Blends of         high acid ionomers with maleic anhydride-grafted polymers are         further disclosed, for example, in U.S. Pat. Nos. 6,992,135 and         6,677,401, the entire disclosures of which are hereby         incorporated herein by reference;     -   (c) a composition comprising a 50/45/5 blend of Surlyn®         8940/Surlyn® 9650/Nucrel® 960, preferably having a material         hardness of from 80 to 85 Shore C;     -   (d) a composition comprising a 50/25/25 blend of Surlyn®         8940/Surlyn® 9650/Surlyn® 9910, preferably having a material         hardness of about 90 Shore C; and     -   (e) a composition comprising a 50/50 blend of Surlyn®         8940/Surlyn® 9650, preferably having a material hardness of         about 86 Shore C.

Surlyn® 8940 is an E/MAA copolymer in which the MAA acid groups have been partially neutralized with sodium ions. Surlyn® 9650 and Surlyn® 9910 are two different grades of E/MAA copolymer in which the MAA acid groups have been partially neutralized with zinc ions. Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt % methacrylic acid. Surlyn® 8940, Surlyn® 9650, Surlyn® 9910, and Nucrel® 960 are commercially available from E. I. du Pont de Nemours and Company.

Non-limiting examples of preferred inner cover layer materials are shown in the Examples below.

The inner cover layer material may include a flow modifier, such as, but not limited to, Nucrel® acid copolymer resins, and particularly Nucrel® 960. Nucrel® acid copolymer resins are commercially available from E. I. du Pont de Nemours and Company.

The outer cover layer is preferably formed from a composition comprising polyurethane, polyurea, or a copolymer or hybrid of polyurethane/polyurea. The outer cover layer material may be thermoplastic or thermoset.

In a particular embodiment, the cover is a single layer preferably formed from an ionomeric composition. The single layer cover preferably has a surface hardness of 65 Shore D or less, or 60 Shore D or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D and a thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.055 or 0.060 inches and an upper limit of 0.065 or 0.080 or 0.090 or 0.100 or 0.110 or 0.120 or 0.140 inches. The flexural modulus of the cover, as measured by ASTM D6272-98 Procedure B, is preferably 500 psi or greater, or from 500 psi to 150,000 psi.

In another particular embodiment, the cover is a two-layer cover consisting of an inner cover layer and an outer cover layer. The inner cover layer is preferably formed from an ionomeric composition and preferably has a surface hardness of 60 Shore D or greater, or 65 Shore D or greater, or a surface hardness within a range having a lower limit of 30 or 40 or 55 or 60 or 65 Shore D and an upper limit of 66 or 68 or 70 or 75 Shore D, and a thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.100 or 0.110 or 0.120 inches. The inner cover layer composition preferably has a material hardness of 95 Shore C or less, or less than 95 Shore C, or 92 Shore C or less, or 90 Shore C or less, or has a material hardness within a range having a lower limit of 70 or 75 or 80 or 84 or 85 Shore C and an upper limit of 90 or 92 or 95 Shore C. The outer cover layer is preferably formed from a castable or reaction injection moldable polyurethane, polyurea, or copolymer or hybrid of polyurethane/polyurea. Such cover material is preferably thermosetting, but may be thermoplastic. The outer cover layer composition preferably has a material hardness of 85 Shore C or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D. The outer cover layer preferably has a surface hardness within a range having a lower limit of 20 or 30 or 35 or 40 Shore D and an upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. The outer cover layer preferably has a thickness within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115 inches. The two-layer cover preferably has an overall thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.055 or 0.060 inches and an upper limit of 0.065 or 0.075 or 0.080 or 0.090 or 0.100 or 0.110 or 0.120 or 0.140 inches.

In another particular embodiment, the cover is a dual-layer cover comprising an inner cover layer and an outer cover layer. In a particular aspect of this embodiment, the surface hardness of the outer core layer is greater than the material hardness of the inner cover layer. In another particular aspect of this embodiment, the surface hardness of the outer core layer is greater than both the inner cover layer and the outer cover layer. The inner cover layer preferably has a material hardness of 95 Shore C or less, or less than 95 Shore C, or 92 Shore C or less, or 90 Shore C or less, or has a material hardness within a range having a lower limit of 70 or 75 or 80 or 84 or 85 Shore C and an upper limit of 90 or 92 or 95 Shore C. The thickness of the inner cover layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.045 or 0.080 or 0.120 inches. The outer cover layer preferably has a material hardness of 85 Shore C or less. The thickness of the outer cover layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.055 or 0.080 inches.

A moisture vapor barrier layer is optionally employed between the core and the cover. Moisture vapor barrier layers are further disclosed, for example, in U.S. Pat. Nos. 6,632,147, 6,932,720, 7,004,854, and 7,182,702, the entire disclosures of which are hereby incorporated herein by reference.

The present invention is not limited by any particular process for forming the golf ball layer(s). It should be understood that the layer(s) can be formed by any suitable technique, including injection molding, compression molding, casting, and reaction injection molding.

When injection molding is used, the composition is typically in a pelletized or granulated form that can be easily fed into the throat of an injection molding machine wherein it is melted and conveyed via a screw in a heated barrel at temperatures of from 150° F. to 600° F., preferably from 200° F. to 500° F. The molten composition is ultimately injected into a closed mold cavity, which may be cooled, at ambient or at an elevated temperature, but typically the mold is cooled to a temperature of from 50° F. to 70° F. After residing in the closed mold for a time of from 1 second to 300 seconds, preferably from 20 seconds to 120 seconds, the core and/or core plus one or more additional core or cover layers is removed from the mold and either allowed to cool at ambient or reduced temperatures or is placed in a cooling fluid such as water, ice water, dry ice in a solvent, or the like.

When compression molding is used to form a center, the composition is first formed into a preform or slug of material, typically in a cylindrical or roughly spherical shape at a weight slightly greater than the desired weight of the molded core. Prior to this step, the composition may be first extruded or otherwise melted and forced through a die after which it is cut into a cylindrical preform. It is that preform that is then placed into a compression mold cavity and compressed at a mold temperature of from 150° F. to 400° F., preferably from 250° F. to 350° F., and more preferably from 260° F. to 295° F. When compression molding a core or cover layer of an HNP composition, a half-shell is first formed via injection molding and then a core comprising one or more layers is enclosed within two half shells and then compression molded in a similar manner to the process previously described.

Reaction injection molding processes are further disclosed, for example, in U.S. Pat. Nos. 6,083,119, 7,338,391, 7,282,169, 7,281,997 and U.S. Patent Application Publication No. 2006/0247073, the entire disclosures of which are hereby incorporated herein by reference.

Golf balls of the present invention typically have a compression of 120 or less, or a compression within a range having a lower limit of 40 or 50 or 60 or 65 or 75 or 80 or 90 and an upper limit of 95 or 100 or 105 or 110 or 115 or 120. Golf balls of the present invention typically have a COR at 125 ft/s of at least 0.70, preferably at least 0.75, more preferably at least 0.78, and even more preferably at least 0.79.

Golf balls of the present invention will typically have dimple coverage of 60% or greater, preferably 65% or greater, and more preferably 75% or greater. The United States Golf Association specifications limit the minimum size of a competition golf ball to 1.680 inches. There is no specification as to the maximum diameter, and golf balls of any size can be used for recreational play. Golf balls of the present invention can have an overall diameter of any size. The preferred diameter of the present golf balls is from 1.680 inches to 1.800 inches. More preferably, the present golf balls have an overall diameter of from 1.680 inches to 1.760 inches, and even more preferably from 1.680 inches to 1.740 inches.

Golf balls of the present invention preferably have a moment of inertia (“MOI”) of 70-95 g·cm², preferably 75-93 g·cm², and more preferably 76-90 g·cm². For low MOI embodiments, the golf ball preferably has an MOI of 85 g·cm² or less, or 83 g·cm² or less. For high MOI embodiment, the golf ball preferably has an MOI of 86 g·cm² or greater, or 87 g·cm² or greater. MOI is measured on a model MOI-005-104 Moment of Inertia Instrument manufactured by Inertia Dynamics of Collinsville, Conn. The instrument is connected to a PC for communication via a COMM port and is driven by MOI Instrument Software version #1.2.

Thermoplastic layers herein may be treated in such a manner as to create a positive or negative hardness gradient. In golf ball layers of the present invention wherein a thermosetting rubber is used, gradient-producing processes and/or gradient-producing rubber formulation may be employed. Gradient-producing processes and formulations are disclosed more fully, for example, in U.S. patent application Ser. No. 12/048,665, filed on Mar. 14, 2008; Ser. No. 11/829,461, filed on Jul. 27, 2007; Ser. No. 11/772,903, filed Jul. 3, 2007; Ser. No. 11/832,163, filed Aug. 1, 2007; Ser. No. 11/832,197, filed on Aug. 1, 2007; the entire disclosure of each of these references is hereby incorporated herein by reference.

In addition to the materials disclosed above, any of the core or cover layers may comprise one or more of the following materials: thermoplastic elastomer, thermoset elastomer, synthetic rubber, thermoplastic vulcanizate, copolymeric ionomer, terpolymeric ionomer, polycarbonate, polyolefin, polyamide, copolymeric polyamide, polyesters, polyester-amides, polyether-amides, polyvinyl alcohols, acryl onitrile-butadiene-styrene copolymers, polyarylate, polyacrylate, polyphenylene ether, impact-modified polyphenylene ether, high impact polystyrene, diallyl phthalate polymer, metallocene-catalyzed polymers, styrene-acrylonitrile (SAN), olefin-modified SAN, acrylonitrile-styrene-acrylonitrile, styrene-maleic anhydride (S/MA) polymer, styrenic copolymer, functionalized styrenic copolymer, functionalized styrenic terpolymer, styrenic terpolymer, cellulose polymer, liquid crystal polymer (LCP), ethylene-propylene-diene rubber (EPDM), ethylene-vinyl acetate copolymer (EVA), ethylene propylene rubber (EPR), ethylene vinyl acetate, polyurea, and polysiloxane. Suitable polyamides for use as an additional material in compositions disclosed herein also include resins obtained by: (1) polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid or 1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, or decamethylenediamine, 1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-opening polymerization of cyclic lactam, such as ξ-caprolactam or ω-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid or 12-aminododecanoic acid; or (4) copolymerzation of a cyclic lactam with a dicarboxylic acid and a diamine. Specific examples of suitable polyamides include Nylon 6, Nylon 66, Nylon 610, Nylon 11, Nylon 12, copolymerized Nylon, Nylon MXD6, and Nylon 46.

In embodiments of the present invention wherein at least one layer is formed from a rubber composition, suitable rubber compositions include natural and synthetic rubbers, including, but not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic block copolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber, halobutyl rubber, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and combinations of two or more thereof. Diene rubbers are preferred, particularly polybutadienes and mixtures of polybutadiene with other elastomers, and especially 1,4-polybutadiene having a cis-structure of at least 40%. In a particularly preferred embodiment, the rubber composition is a reaction product of a diene rubber, a crosslinking agent, a filler, a co-crosslinking agent or free radical initiator, and optionally a cis-to-trans catalyst. The rubber is preferably selected from polybutadiene and styrene-butadiene. The crosslinking agent typically includes a metal salt, such as a zinc-, aluminum-, sodium-, lithium-, nickel-, calcium-, or magnesium salt, of an unsaturated fatty acid or monocarboxylic acid, such as (meth) acrylic acid. Preferred crosslinking agents include zinc acrylate, zinc diacrylate (ZDA), zinc methacrylate, and zinc dimethacrylate (ZDMA), and mixtures thereof. The crosslinking agent is present in an amount sufficient to crosslink a portion of the chains of the polymers in the composition. The crosslinking agent is generally present in the rubber composition in an amount of from 15 to 30 phr, or from 19 to 25 phr, or from 20 to 24 phr. The desired compression may be obtained by adjusting the amount of crosslinking, which can be achieved, for example, by altering the type and amount of crosslinking agent. The free radical initiator can be any known polymerization initiator which decomposes during the cure cycle, including, but not limited to, dicumyl peroxide, 1,1-di-(t-butylperoxy) 3,3,5-trimethyl cyclohexane, a-a bis-(t-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5 di-(t-butylperoxy) hexane or di-t-butyl peroxide, and mixtures thereof. The rubber composition optionally contains one or more antioxidants. Antioxidants are compounds that can inhibit or prevent the oxidative degradation of the rubber. Suitable antioxidants include, for example, dihydroquinoline antioxidants, amine type antioxidants, and phenolic type antioxidants. The rubber composition may also contain one or more fillers to adjust the density and/or specific gravity of the core or cover. Fillers are typically polymeric or mineral particles. Exemplary fillers include precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates (e.g., calcium carbonate and magnesium carbonate), metals (e.g., titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin), metal alloys (e.g., steel, brass, bronze, boron carbide whiskers, and tungsten carbide whiskers), metal oxides (e.g., zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide, and zirconium oxide), particulate carbonaceous materials (e.g., graphite, carbon black, cotton flock, natural bitumen, cellulose flock, and leather fiber), microballoons (e.g., glass and ceramic), fly ash, regrind, nanofillers and combinations thereof. The rubber composition may also contain one or more additives selected from free radical scavengers, accelerators, scorch retarders, coloring agents, fluorescent agents, chemical blowing and foaming agents, defoaming agents, stabilizers, softening agents, impact modifiers, plasticizers, and the like. The rubber composition may also contain a soft and fast agent, such as those disclosed in U.S. patent application Ser. No. 11/972,240, the entire disclosure of which is hereby incorporated herein by reference. Examples of commercially available polybutadienes suitable for use in forming golf ball core layers of the present invention include, but are not limited to, Buna CB23, commercially available from LANXESS Corporation; SE BR-1220, commercially available from The Dow Chemical Company; Europrene® NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa; UBEPOL-BR® rubbers, commercially available from UBE Industries, Ltd.; and BR 01 commercially available from Japan Synthetic Rubber Co., Ltd. Suitable types and amounts of rubber, crosslinking agent, filler, co-crosslinking agent, initiator and additives are more fully described in, for example, U.S. Patent Application Publication No. 2004/0214661, 2003/0144087, and 2003/0225197, and U.S. Pat. Nos. 6,566,483, 6,695,718, and 6,939,907, the entire disclosures of which are hereby incorporated herein by reference.

In embodiments of the present invention wherein at least one layer is formed from a conventional HNP composition, suitable HNP compositions comprise an HNP and optionally additives, fillers, and/or melt flow modifiers. Suitable HNPs are salts of homopolymers and copolymers of α,β-ethylenically unsaturated mono- or dicarboxylic acids, and combinations thereof, optionally including a softening monomer. The acid polymer is neutralized to 70% or higher, including up to 100%, with a suitable cation source. Suitable additives and fillers include, for example, blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nanofillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, acid copolymer wax, surfactants; inorganic fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay, silica, lead silicate, and the like; high specific gravity metal powder fillers, such as tungsten powder, molybdenum powder, and the like; regrind, i.e., core material that is ground and recycled; and nano-fillers. Suitable melt flow modifiers include, for example, fatty acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof. Suitable HNP compositions also include blends of HNPs with partially neutralized ionomers as disclosed, for example, in U.S. Patent Application Publication No. 2006/0128904, the entire disclosure of which is hereby incorporated herein by reference, and blends of HNPs with additional thermoplastic and thermoset materials, including, but not limited to, ionomers, acid copolymers, engineering thermoplastics, fatty acid/salt-based highly neutralized polymers, polybutadienes, polyurethanes, polyesters, thermoplastic elastomers, and other conventional polymeric materials. Suitable HNP compositions are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated herein by reference.

Other preferred materials suitable for use as an additional material in golf ball compositions disclosed herein include Skypel polyester elastomers, commercially available from SK Chemicals of South Korea; Septon® diblock and triblock copolymers, commercially available from Kuraray Corporation of Kurashiki, Japan; and Kraton® diblock and triblock copolymers, commercially available from Kraton Polymers LLC of Houston, Tex.

Ionomers are also well suited for blending with compositions disclosed herein. Suitable ionomeric polymers include α-olefin/unsaturated carboxylic acid copolymer- or terpolymer-type ionomeric resins. Copolymeric ionomers are obtained by neutralizing at least a portion of the carboxylic groups in a copolymer of an α-olefin and an α,β-unsaturated carboxylic acid having from 3 to 8 carbon atoms, with a metal ion. Terpolymeric ionomers are obtained by neutralizing at least a portion of the carboxylic groups in a terpolymer of an α-olefin, an α,β-unsaturated carboxylic acid having from 3 to 8 carbon atoms, and an α,β-unsaturated carboxylate having from 2 to 22 carbon atoms, with a metal ion. Examples of suitable α-olefins for copolymeric and terpolymeric ionomers include ethylene, propylene, 1-butene, and 1-hexene. Examples of suitable unsaturated carboxylic acids for copolymeric and terpolymeric ionomers include acrylic, methacrylic, ethacrylic, α-chloroacrylic, crotonic, maleic, fumaric, and itaconic acid. Copolymeric and terpolymeric ionomers include ionomers having varied acid contents and degrees of acid neutralization, neutralized by monovalent or bivalent cations as disclosed herein. Examples of commercially available ionomers suitable for blending with compositions disclosed herein include Surlyn® ionomer resins, commercially available from E. I. du Pont de Nemours and Company, and Iotek® ionomers, commercially available from ExxonMobil Chemical Company.

Silicone materials are also well suited for blending with compositions disclosed herein. Suitable silicone materials include monomers, oligomers, prepolymers, and polymers, with or without adding reinforcing filler. One type of silicone material that is suitable can incorporate at least 1 alkenyl group having at least 2 carbon atoms in their molecules. Examples of these alkenyl groups include, but are not limited to, vinyl, allyl, butenyl, pentenyl, hexenyl, and decenyl. The alkenyl functionality can be located at any location of the silicone structure, including one or both terminals of the structure. The remaining (i.e., non-alkenyl) silicon-bonded organic groups in this component are independently selected from hydrocarbon or halogenated hydrocarbon groups that contain no aliphatic unsaturation. Non-limiting examples of these include: alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, and hexyl; cycloalkyl groups, such as cyclohexyl and cycloheptyl; aryl groups, such as phenyl, tolyl, and xylyl; aralkyl groups, such as benzyl and phenethyl; and halogenated alkyl groups, such as 3,3,3-trifluoropropyl and chloromethyl. Another type of suitable silicone material is one having hydrocarbon groups that lack aliphatic unsaturation. Specific examples include: trimethylsiloxy-endblocked dimethyl siloxane-methylhexenylsiloxane copolymers; dimethylhexenylsiloxy-endblocked dimethyl siloxane-methylhexenylsiloxane copolymers; trimethylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane copolymers; trimethylsiloxyl-endblocked methylphenylsiloxane-dimethylsiloxane-methylvinysiloxane copolymers; dimethylvinylsiloxy-endblocked dimethylpolysiloxanes; dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane copolymers; dimethylvinylsiloxy-endblocked methylphenylpolysiloxanes; dimethylvinylsiloxy-endblocked methylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane copolymers; and the copolymers listed above wherein at least one group is dimethylhydroxysiloxy. Examples of commercially available silicones suitable for blending with compositions disclosed herein include Silastic® silicone rubber, commercially available from Dow Corning Corporation of Midland, Mich.; Blensil® silicone rubber, commercially available from General Electric Company of Waterford, N.Y.; and Elastosil® silicones, commercially available from Wacker Chemie AG of Germany.

Other types of copolymers can also be added to the golf ball compositions disclosed herein. For example, suitable copolymers comprising epoxy monomers include styrene-butadiene-styrene block copolymers in which the polybutadiene block contains an epoxy group, and styrene-isoprene-styrene block copolymers in which the polyisoprene block contains epoxy. Examples of commercially available epoxy functionalized copolymers include ESBS A1005, ESBS A1010, ESBS A1020, ESBS AT018, and ESBS AT019 epoxidized styrene-butadiene-styrene block copolymers, commercially available from Daicel Chemical Industries, Ltd. of Japan.

Ionomeric compositions used to form golf ball layers of the present invention can be blended with non-ionic thermoplastic resins, particularly to manipulate product properties. Examples of suitable non-ionic thermoplastic resins include, but are not limited to, polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea, Pebax® thermoplastic polyether block amides commercially available from Arkema Inc., styrene-butadiene-styrene block copolymers, styrene(ethylene-butylene)-styrene block copolymers, polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-(meth)acrylate, ethylene-(meth)acrylic acid, functionalized polymers with maleic anhydride grafting, epoxidation, etc., elastomers (e.g., EPDM, metallocene-catalyzed polyethylene) and ground powders of the thermoset elastomers.

Also suitable for forming the center and outer core layers are the compositions having high COR when formed into solid spheres disclosed in U.S. Patent Application Publication No. 2003/0130434 and U.S. Pat. No. 6,653,382, the entire disclosures of which are hereby incorporated herein by reference. Reference is also made to U.S. Patent Application Publication No. 2003/0144087 for various ball constructions and materials that can be used in golf ball core, intermediate, and cover layers.

Additional materials suitable for forming the core layers include the core compositions disclosed in U.S. Pat. No. 7,300,364, the entire disclosure of which is hereby incorporated herein by reference. For example, suitable core materials include HNPs neutralized with organic fatty acids and salts thereof, metal cations, or a combination of both. In addition to HNPs neutralized with organic fatty acids and salts thereof, core compositions may comprise at least one rubber material having a resilience index of at least about 40. Preferably the resilience index is at least about 50. Polymers that produce resilient golf balls and, therefore, are suitable for the present invention, include but are not limited to CB23, CB22, commercially available from of Bayer Corp. of Orange, Tex., BR60, commercially available from Enichem of Italy, and 1207G, commercially available from Goodyear Corp. of Akron, Ohio Additionally, the unvulcanized rubber, such as polybutadiene, in golf balls prepared according to the invention typically has a Mooney viscosity of between about 40 and about 80, more preferably, between about 45 and about 65, and most preferably, between about 45 and about 55. Mooney viscosity is typically measured according to ASTM-D1646.

In addition to the above materials, the center can be formed from a low deformation material selected from metal, rigid plastics, polymers reinforced with high strength organic or inorganic fillers or fibers, and blends and composites thereof. Suitable low deformation materials also include those disclosed in U.S. Patent Application Publication No. 2005/0250600, the entire disclosure of which is hereby incorporated herein by reference.

Examples

It should be understood that the examples below are for illustrative purposes only. In no manner is the present invention limited to the specific disclosures herein.

Additional Examples of Suitable HNPs

The HNPs of Table 3 below have been found to be particularly useful as the relatively soft/low modulus HNP and/or the relatively hard/high modulus HNP of the present invention.

TABLE 3 Flexural Hardness**, Hardness**, cation Modulus*, Shore C Shore D Example source psi (18 day) (annealed) 1 Ca/Mg 71,600 88 57 2 Ca/Li 70,300 89 58 3 Ca 70,100 92 60 4 Ca/Zn 60,400 88 58 5 Mg 38,300 84 52 6 Mg 27,600 84 52 7 Mg 16,300 78 45 8 Mg 10,600 70 40 9 Mg 10,400 69 39 *Flexural modulus was measured according to ASTM D790-03 Procedure B. **Hardness was measured according to ASTM D2240.

In embodiments of the present invention directed to a golf ball having center formed from a relatively soft HNP composition, Examples 6-9 are particularly suitable for use as the relatively soft HNP composition.

In embodiments of the present invention directed to a golf ball having an outer core layer formed from a relatively soft HNP composition, Examples 5-9 are particularly suitable for use as the relatively soft HNP composition.

In embodiments of the present invention directed to a golf ball having a center formed from a relatively hard HNP composition, Examples 1-6 are particularly suitable for use as the relatively hard HNP composition.

In embodiments of the present invention directed to a golf ball having an outer core layer formed from a relatively hard HNP composition, Examples 1-4 are particularly suitable for use as the relatively hard HNP composition.

In embodiments of the present invention directed to a golf ball having center formed from a low modulus HNP composition, Examples 6-9 are particularly suitable for use as the low modulus HNP composition.

In embodiments of the present invention directed to a golf ball having an outer core layer formed from a low modulus HNP composition, Examples 5-9 are particularly suitable for use as the low modulus HNP composition.

In embodiments of the present invention directed to a golf ball having a center formed from a high modulus HNP composition, Examples 1-6 are particularly suitable for use as the high modulus HNP composition.

In embodiments of the present invention directed to a golf ball having an outer core layer formed from a high modulus HNP composition, Examples 1-4 are particularly suitable for use as the high modulus HNP composition.

Additional Examples of Suitable Ionomeric Cover Layer Compositions

Twelve ionomeric inner cover layer compositions according to the present invention were prepared by melt blending Surlyn® 8150 and Fusabond® 572D in a twin screw extruder, at a temperature of at least 450° F. (230° C.). The relative amounts of each component used are indicated in Table 4 below.

Flex bars of each blend composition were formed and evaluated for hardness according to ASTM D2240 following 10 days of aging at 50% relative humidity and 23° C. The results are reported in Table 4 below.

TABLE 4 Fusabond ® Shore C Surlyn ® 8150, 572D, Hardness at Example wt % wt % 10 Days 1 89 11 91.2 2 84 16 89.8 3 84 16 90.4 4 84 16 89.6 5 81 19 88.9 6 80 20 89.1 7 78 22 88.1 8 76 24 87.6 9 76 24 87.2 10 73 27 86.6 11 71 29 86.7 12 67 33 84.0

The following commercially available materials were used in the below examples:

-   -   A-C® 5120 ethylene acrylic acid copolymer with an acrylic acid         content of 15%,     -   A-C® 5180 ethylene acrylic acid copolymer with an acrylic acid         content of 20%,     -   A-C® 395 high density oxidized polyethylene homopolymer, and     -   A-C® 575 ethylene maleic anhydride copolymer, commercially         available from Honeywell;     -   CB23 high-cis neodymium-catalyzed polybutadiene rubber,         commercially available from Lanxess Corporation;     -   CA1700 Soya fatty acid, CA1726 linoleic acid, and CA1725         conjugated linoleic acid, commercially available from Chemical         Associates;     -   Century® 1107 highly purified isostearic acid mixture of         branched and straight-chain C18 fatty acid, commercially         available from Arizona Chemical;     -   Clarix® 011370-01 ethylene acrylic acid copolymer with an         acrylic acid content of 13% and     -   Clarix® 011536-01 ethylene acrylic acid copolymer with an         acrylic acid content of 15%, commercially available from A.         Schulman Inc.;     -   Elvaloy® AC 1224 ethylene-methyl acrylate copolymer with a         methyl acrylate content of 24 wt %,     -   Elvaloy® AC 1335 ethylene-methyl acrylate copolymer with a         methyl acrylate content of 35 wt %,     -   Elvaloy® AC 2116 ethylene-ethyl acrylate copolymer with an ethyl         acrylate content of 16 wt %,     -   Elvaloy® AC 3427 ethylene-butyl acrylate copolymer having a         butyl acrylate content of 27 wt %, and     -   Elvaloy® AC 34035 ethylene-butyl acrylate copolymer having a         butyl acrylate content of 35 wt %, commercially available         from E. I. du Pont de Nemours and Company;     -   Escor® AT-320 ethylene acid terpolymer, commercially available         from ExxonMobil Chemical Company;     -   Exxelor® VA 1803 amorphous ethylene copolymer functionalized         with maleic anhydride, commercially available from ExxonMobil         Chemical Company;     -   Fusabond® N525 metallocene-catalyzed polyethylene,     -   Fusabond® N416 chemically modified ethylene elastomer,     -   Fusabond® C190 anhydride modified ethylene vinyl acetate         copolymer, and     -   Fusabond® P614 functionalized polypropylene, commercially         available from E. I. du Pont de Nemours and Company;     -   Hytrel® 3078 very low modulus thermoplastic polyester elastomer,         commercially available from E. I. du Pont de Nemours and         Company;     -   Kraton® FG 1901 GT linear triblock copolymer based on styrene         and ethylene/butylene with a polystyrene content of 30% and     -   Kraton® FG1924GT linear triblock copolymer based on styrene and         ethylene/butylene with a polystyrene content of 13%,         commercially available from Kraton Performance Polymers Inc.;     -   Lotader® 4603, 4700 and 4720, random copolymers of ethylene,         acrylic ester and maleic anhydride, commercially available from         Arkema Corporation;     -   Nordel® IP 4770 high molecular weight semi-crystalline EPDM         rubber, commercially available from The Dow Chemical Company;     -   Nucrel® 9-1, Nucrel® 599, Nucrel® 960, Nucrel® 0407, Nucrel®         0609, Nucrel® 1214, Nucrel® 2906, Nucrel® 2940, Nucrel® 30707,         Nucrel® 31001, and Nucrel® AE acid copolymers, commercially         available from E. I. du Pont de Nemours and Company;     -   Primacor® 3150, 3330, 59801, and 59901 acid copolymers,         commercially available from The Dow Chemical Company;     -   Royaltuf® 498 maleic anhydride modified polyolefin based on an         amorphous EPDM, commercially available from Chemtura         Corporation;     -   Sylfat® FA2 tall oil fatty acid, commercially available from         Arizona Chemical;     -   Vamac® G terpolymer of ethylene, methylacrylate and a cure site         monomer, commercially available from E. I. du Pont de Nemours         and Company; and     -   XUS 60758.08L ethylene acrylic acid copolymer with an acrylic         acid content of 13.5%, commercially available from The Dow         Chemical Company.

Various compositions were melt blended using components as given in Table 5 below. The compositions were neutralized by adding a cation source in an amount sufficient to neutralize, theoretically, 110% of the acid groups present in components 1 and 3, except for example 72, in which the cation source was added in an amount sufficient to neutralize 75% of the acid groups. Magnesium hydroxide was used as the cation source, except for example 68, in which magnesium hydroxide and sodium hydroxide were used in an equivalent ratio of 4:1. In addition to components 1-3 and the cation source, example 71 contains ethyl oleate plasticizer.

The relative amounts of component 1 and component 2 used are indicated in Table 5 below, and are reported in wt %, based on the combined weight of components 1 and 2. The relative amounts of component 3 used are indicated in Table 5 below, and are reported in wt %, based on the total weight of the composition.

TABLE 5 Example Component 1 wt % Component 2 wt % Component 3 wt % 1 Primacor 5980I 78 Lotader 4603 22 magnesium oleate 41.6 2 Primacor 5980I 84 Elvaloy AC 1335 16 magnesium oleate 41.6 3 Primacor 5980I 78 Elvaloy AC 3427 22 magnesium oleate 41.6 4 Primacor 5980I 78 Elvaloy AC 1335 22 magnesium oleate 41.6 5 Primacor 5980I 78 Elvaloy AC 1224 22 magnesium oleate 41.6 6 Primacor 5980I 78 Lotader 4720 22 magnesium oleate 41.6 7 Primacor 5980I 85 Vamac G 15 magnesium oleate 41.6 8 Primacor 5980I 90 Vamac G 10 magnesium oleate 41.6 8.1 Primacor 5990I 90 Fusabond 614 10 magnesium oleate 41.6 9 Primacor 5980I 78 Vamac G 22 magnesium oleate 41.6 10 Primacor 5980I 75 Lotader 4720 25 magnesium oleate 41.6 11 Primacor 5980I 55 Elvaloy AC 3427 45 magnesium oleate 41.6 12 Primacor 5980I 55 Elvaloy AC 1335 45 magnesium oleate 41.6 12.1 Primacor 5980I 55 Elvaloy AC 34035 45 magnesium oleate 41.6 13 Primacor 5980I 55 Elvaloy AC 2116 45 magnesium oleate 41.6 14 Primacor 5980I 78 Elvaloy AC 34035 22 magnesium oleate 41.6 14.1 Primacor 5990I 80 Elvaloy AC 34035 20 magnesium oleate 41.6 15 Primacor 5980I 34 Elvaloy AC 34035 66 magnesium oleate 41.6 16 Primacor 5980I 58 Vamac G 42 magnesium oleate 41.6 17 Primacor 5990I 80 Fusabond 416 20 magnesium oleate 41.6 18 Primacor 5980I 100 — — magnesium oleate 41.6 19 Primacor 5980I 78 Fusabond 416 22 magnesium oleate 41.6 20 Primacor 5990I 100 — — magnesium oleate 41.6 21 Primacor 5990I 20 Fusabond 416 80 magnesium oleate 41.6 21.1 Primacor 5990I 20 Fusabond 416 80 magnesium oleate 31.2 21.2 Primacor 5990I 20 Fusabond 416 80 magnesium oleate 20.8 22 Clarix 011370 30.7 Fusabond 416 69.3 magnesium oleate 41.6 23 Primacor 5990I 20 Royaltuf 498 80 magnesium oleate 41.6 24 Primacor 5990I 80 Royaltuf 498 20 magnesium oleate 41.6 25 Primacor 5990I 80 Kraton FG1924GT 20 magnesium oleate 41.6 26 Primacor 5990I 20 Kraton FG1924GT 80 magnesium oleate 41.6 27 Nucrel 30707 57 Fusabond 416 43 magnesium oleate 41.6 28 Primacor 5990I 80 Hytrel 3078 20 magnesium oleate 41.6 29 Primacor 5990I 20 Hytrel 3078 80 magnesium oleate 41.6 30 Primacor 5980I 26.8 Elvaloy AC 34035 73.2 magnesium oleate 41.6 31 Primacor 5980I 26.8 Lotader 4603 73.2 magnesium oleate 41.6 32 Primacor 5980I 26.8 Elvaloy AC 2116 73.2 magnesium oleate 41.6 33 Escor AT-320 30 Elvaloy AC 34035 52 magnesium oleate 41.6 Primacor 5980I 18 34 Nucrel 30707 78.5 Elvaloy AC 34035 21.5 magnesium oleate 41.6 35 Nucrel 30707 78.5 Fusabond 416 21.5 magnesium oleate 41.6 36 Primacor 5980I 26.8 Fusabond 416 73.2 magnesium oleate 41.6 37 Primacor 5980I 19.5 Fusabond N525 80.5 magnesium oleate 41.6 38 Clarix 011536-01 26.5 Fusabond N525 73.5 magnesium oleate 41.6 39 Clarix 011370-01 31 Fusabond N525 69 magnesium oleate 41.6 39.1 XUS 60758.08L 29.5 Fusabond N525 70.5 magnesium oleate 41.6 40 Nucrel 31001 42.5 Fusabond N525 57.5 magnesium oleate 41.6 41 Nucrel 30707 57.5 Fusabond N525 42.5 magnesium oleate 41.6 42 Escor AT-320 66.5 Fusabond N525 33.5 magnesium oleate 41.6 43 Nucrel 2906/2940 21 Fusabond N525 79 magnesium oleate 41.6 44 Nucrel 960 26.5 Fusabond N525 73.5 magnesium oleate 41.6 45 Nucrel 1214 33 Fusabond N525 67 magnesium oleate 41.6 46 Nucrel 599 40 Fusabond N525 60 magnesium oleate 41.6 47 Nucrel 9-1 44.5 Fusabond N525 55.5 magnesium oleate 41.6 48 Nucrel 0609 67 Fusabond N525 33 magnesium oleate 41.6 49 Nucrel 0407 100 — — magnesium oleate 41.6 50 Primacor 5980I 90 Fusabond N525 10 magnesium oleate 41.6 51 Primacor 5980I 80 Fusabond N525 20 magnesium oleate 41.6 52 Primacor 5980I 70 Fusabond N525 30 magnesium oleate 41.6 53 Primacor 5980I 60 Fusabond N525 40 magnesium oleate 41.6 54 Primacor 5980I 50 Fusabond N525 50 magnesium oleate 41.6 55 Primacor 5980I 40 Fusabond N525 60 magnesium oleate 41.6 56 Primacor 5980I 30 Fusabond N525 70 magnesium oleate 41.6 57 Primacor 5980I 20 Fusabond N525 80 magnesium oleate 41.6 58 Primacor 5980I 10 Fusabond N525 90 magnesium oleate 41.6 59 — — Fusabond N525 100 magnesium oleate 41.6 60 Nucrel 0609 40 Fusabond N525 20 magnesium oleate 41.6 Nucrel 0407 40 61 Nucrel AE 100 — — magnesium oleate 41.6 62 Primacor 5980I 30 Fusabond N525 70 CA1700 soya fatty acid 41.6 magnesium salt 63 Primacor 5980I 30 Fusabond N525 70 CA1726 linoleic acid 41.6 magnesium salt 64 Primacor 5980I 30 Fusabond N525 70 CA1725 41.6 conjugated linoleic acid magnesium salt 65 Primacor 5980I 30 Fusabond N525 70 Century 1107 41.6 isostearic acid magnesium salt 66 A-C 5120 73.3 Lotader 4700 26.7 oleic acid 41.6 magnesium salt 67 A-C 5120 73.3 Elvaloy 34035 26.7 oleic acid 41.6 magnesium salt 68 Primacor 5980I 78.3 Lotader 4700 21.7 oleic acid 41.6 magnesium salt and sodium salt 69 Primacor 5980I 47 Elvaloy AC34035 13 — — A-C 5180 40 70 Primacor 5980I 30 Fusabond N525 70 Sylfat FA2 41.6 magnesium salt 71 Primacor 5980I 30 Fusabond N525 70 oleic acid 31.2 magnesium salt 10 ethyl oleate 72 Primacor 5980I 80 Fusabond N525 20 sebacic acid 41.6 magnesium salt 73 Primacor 5980I 60 — — — — A-C 5180 40 74 Primacor 5980I 78.3 — — oleic acid 41.6 A-C 575 21.7 magnesium salt 75 Primacor 5980I 78.3 Exxelor VA 1803 21.7 oleic acid 41.6 magnesium salt 76 Primacor 5980I 78.3 A-C 395 21.7 oleic acid 41.6 magnesium salt 77 Primacor 5980I 78.3 Fusabond C190 21.7 oleic acid 41.6 magnesium salt 78 Primacor 5980I 30 Kraton FG 1901 70 oleic acid 41.6 magnesium salt 79 Primacor 5980I 30 Royaltuf 498 70 oleic acid 41.6 magnesium salt 80 A-C 5120 40 Fusabond N525 60 oleic acid 41.6 magnesium salt 81 Primacor 5980I 30 Fusabond N525 70 erucic acid 41.6 magnesium salt 82 Primacor 5980I 30 CB23 70 oleic acid 41.6 magnesium salt 83 Primacor 5980I 30 Nordel IP 4770 70 oleic acid 41.6 magnesium salt 84 Primacor 5980I 48 Fusabond N525 20 oleic acid 41.6 A-C 5180 32 magnesium salt 85 Nucrel 2806 22.2 Fusabond N525 77.8 oleic acid 41.6 magnesium salt 86 Primacor 3330 61.5 Fusabond N525 38.5 oleic acid 41.6 magnesium salt 87 Primacor 3330 45.5 Fusabond N525 20 oleic acid 41.6 Primacor 3150 34.5 magnesium salt 88 Primacor 3330 28.5 — — oleic acid 41.6 Primacor 3150 71.5 magnesium salt 89 Primacor 3150 67 Fusabond N525 33 oleic acid 41.6 magnesium salt 90 Primacor 5980I 55 Elvaloy AC 34035 45 oleic acid 31.2 magnesium salt 10 ethyl oleate

Solid spheres of each composition were injection molded, and the solid sphere COR, compression, Shore D hardness, and Shore C hardness of the resulting spheres were measured after two weeks. The results are reported in Table 6 below. The surface hardness of a sphere is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the sphere or on surface defects, such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface, care must be taken to insure that the sphere is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for all hardness measurements and is set to record the maximum hardness reading obtained for each measurement. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand. The weight on the durometer and attack rate conform to ASTM D-2240.

TABLE 6 Solid Sphere Solid Sphere Solid Sphere Solid Sphere Ex. COR Compression Shore D Shore C 1 0.845 120 59.6 89.2 2 * * * * 3 0.871 117 57.7 88.6 4 0.867 122 63.7 90.6 5 0.866 119 62.8 89.9 6 * * * * 7 * * * * 8 * * * * 8.1 0.869 127 65.3 92.9 9 * * * * 10 * * * * 11 * * * * 12 0.856 101 55.7 82.4 12.1 0.857 105 53.2 81.3 13 * * * * 14 0.873 122 64.0 91.1 14.1 * * * * 15 * * * * 16 * * * * 17 0.878 117 60.1 89.4 18 0.853 135 67.6 94.9 19 * * * * 20 0.857 131 66.2 94.4 21 0.752 26 34.8 57.1 21.1 0.729 9 34.3 56.3 21.2 0.720 2 33.8 55.2 22 * * * * 23 * * * * 24 * * * * 25 * * * * 26 * * * * 27 * * * * 28 * * * * 29 * * * * 30 ** 66 42.7 65.5 31 0.730 67 45.6 68.8 32 ** 100 52.4 78.2 33 0.760 64 43.6 64.5 34 0.814 91 52.8 80.4 35 * * * * 36 * * * * 37 * * * * 38 * * * * 39 * * * * 39.1 * * * * 40 * * * * 41 * * * * 42 * * * * 43 * * * * 44 * * * * 45 * * * * 46 * * * * 47 * * * * 48 * * * * 49 * * * * 50 * * * * 51 0.873 121 61.5 90.2 52 0.870 116 60.4 88.2 53 0.865 107 57.7 84.4 54 0.853 97 53.9 80.2 55 0.837 82 50.1 75.5 56 0.818 66 45.6 70.7 57 0.787 45 41.3 64.7 58 0.768 26 35.9 57.3 59 * * * * 60 * * * * 61 * * * * 62 * * * * 63 * * * * 64 * * * * 65 * * * * 66 * * * * 67 * * * * 68 * * * * 69 * * * * 70 * * * * 71 * * * * 72 * * * * 73 * * * * 74 * * * * 75 * * * * 76 * * * * 77 * * * * 78 * * * * 79 * * * * 80 * * * * 81 * * * * 82 * * * * 83 * * * * 84 * * * * 85 * * * * 86 * * * * 87 * * * * 88 * * * * 89 * * * * 90 * * * * * not measured ** sphere broke during measurement

When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used.

All patents, publications, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains. 

What is claimed is:
 1. A four-piece golf ball consisting of the following four layers: (a) a thermoset rubber center having a diameter of from 1.200 inches to 1.500 inches, a center hardness of from 55 Shore C to 75 Shore C, and a surface hardness of from 45 Shore C to 90 Shore C; (b) a first intermediate layer having a thickness of from 0.032 inches to 0.075 inches and formed from a composition comprising a first acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; (c) a second intermediate layer having a thickness of from 0.032 inches to 0.080 inches, a surface hardness greater than or equal to the surface hardness of the center and the center hardness of the center, and formed from a composition comprising a second acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; and (d) an outer cover layer having a surface hardness of from 58 Shore D to 75 Shore D; wherein at least one of the first intermediate layer composition and the second intermediate layer composition is a plasticized composition comprising from 0.5 wt % to 80 wt %, based on the total weight of the composition, of a plasticizer; and wherein at least one of the first intermediate layer composition and the second intermediate layer composition is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized.
 2. The golf ball of claim 1, wherein the first intermediate layer composition is at least partially neutralized such that at least 70% of all acid groups present in the first intermediate layer composition are neutralized.
 3. The golf ball of claim 1, wherein at least 95% of all acid groups present in the first intermediate layer composition are neutralized.
 4. The golf ball of claim 1, wherein the surface hardness of the second intermediate layer is greater than the surface hardness of the first intermediate layer.
 5. The golf ball of claim 1, wherein the plasticizer is selected from the group consisting of fatty acid esters. 